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THE 

PLURALITY   OF    WORLDS. 


"  Lo,  these  are  parts  of  His  ways :  but  how  little  a  portion 
is  hfcaid  of  Him?  the  thunder  of  His  power  who  cir.  under- 
Btand  ?  "—Jon  xxvi.  14. 


OTHER  WORLDS  THAN  OURSj 


THE   PLURALITY   OF  WORLDS 

STUDIED  UNDER  THE    LIGHT   OF  RECENT 

SCIENTIFIC  RESEARCHES. 


RICHARD  A.  PROCTOR,  B.A.,  F.R.A.S., 

IUTHOB  or  "SATURN  AND  ITS  SYSTEM,''"'' SUN-VIEWS  or  THE  EARTH. 

"  HALF-HOURS  WITH   THE  TELESCOPE,"   ETC. 


Not  to  this  evanescent  speck  of  earth 
Poorly  confined— the  radiant  tracts  on  high 
Are  our  exalted  range ;  intent  to  gaze 
Creation  through,  aud  from  that  full  complex 
Of  never-ending  wonders,  to  conceive 
Of  the  SOLE  BEING  right.  THOMSON. 


NEW  YORK . 
D.    APPLETON   AND   COMPANY, 

1,   3,   AND   5   BOND    STREET. 
1886. 


P5L 


SI 

P?83 


PREFACE. 


THE  GENERAL  PURPOSE  I  liave  liad  in  view  in  writ- 
ing the  present  treatise  wirl  be  gathered  from  the 
iatroductory  pages;  but  I  wish  to  offer  here  a  few 
remarks  on  certain  points  of  detail. 

It  will  be  seen  that,  on  many  of  the  subjects  dealt 
with  in  this  work,  I  have  propounded  views  which 
differ  from  those  usually  accepted.  I  have  not  done 
this  from  any  love  of  novelty,  nor  from  any  desire  to 
attract  attention  by  bizarre  or  fanciful  theories.  Each, 
of  the  new  views  here  presented  has  been  the  result 
of  a  careful  study  of  the  subject  dealt  with,  and  I  have 
searched  as  anxiously  for  considerations  opposed  to 
any  novel  theory  as  for  arguments  in  its  favor.  If 
others  should  be  more  successful  than  I  have  been  in 
finding  reasons  for  rejecting  any  of  my  views,  I  shall 
be  ready  to  abandon  them  without  regret.  I  trust  I 
am  free  from  that  weakness  which  forces  a  man  to  re- 
gard every  theory  he  has  once  advocated  as  a  matter 


6  PREFACE 

to  be  defended  at  all  hazards.  No  weakness  more 
mischievously  affects  the  work  of  the  student  of 
science.  As  Faraday  said,  "  Truth  should  be  the  pri- 
mary object  of  the  philosopher  ; "  and  this  can  never 
be  the  case  if,  where  he  imagines  he  holds  a  theory, 
the  theory  has  in  truth  possession  of  him. 

Some  among  my  readers  will  recognize,  in  the 
views  here  presented,  the  growth  of  ideas  which  I 
have  dealt  with  consecutively,  with  more  or  less  ful- 
ness, in  the  pages  of  several  quarterly,  monthly,  and 
weekly  serials,  and  in  one  of  our  leading  daily  news- 
papers. I  refer  to  this,  because  it  has  happened  to 
me  several  times  lately  to  be  accused  of  plagiarism, 
when  I  have  had  occasion,  in  developing  fresh  ideas 
on  a  subject,  to  repeat  statements  which  (unknown  of 
course  to  my  accusers)  had  proceeded  from  my  own 
pen.  It  is  not  often  one  is  accused  of  stealing  one's 
own  ideas,  but  that  is  a  pleasure  I  have  more  than 
once  been  enabled  to  enjoy  of  late,  and  I  here  present 
my  compliments  to  those  who  (anonymously  or  other- 
wise) have  afforded  me  that  luxury. 

"Wherever  it  has  been  in  accordance  with  the  cus- 
tom of  any  journal,  however,  I  have  always  written 
under  my  own  name. 

Since  the  manuscript  of  this  work  was  placed  in 
the  printers'  hands,  I  have  obtained  fresh  evidence  on 


PREFACE.  7 

some  ot    the   theories  dealt  with  in  the  following 
pages. 

One  of  the  most  surprising  phenomena  ever  wit- 
nessed by  the  telescopist — a  phenomenon  I  had  read 
of  long  since,  but  had  not  thought  of  in  connection 
with  my  subject — seems  to  me  to  afford  stronger  evi- 
dence than  any  adduced  in  the  text,  in  favor  of  my 
theory  that  the  major  planets  are  subsidiary  suns  sup- 
plying heat  (if  not  a  minute  proportion  of  light  even) 
to  their  satellites.  I  refer  to  the  observation  made  by 
Admiral  Smyth,  that  on  one  occasion  the  second  sat- 
ellite of  Jupiter,  twelve  minutes  after  entering  on  the 
disk  of  the  planet,  was  seen  outside  the  limb,  "  where 
it  remained  four  minutes,  and  then  suddenly  van- 
ished." Two  other  equally  competent  observers, 
Haclear  and  Pearson,  witnessed  the  same  phenome- 
non. "  Here,"  says  Webb,  "  explanation  is  set  at  defi- 
ance." But  it  is  precisely  where  explanation  seems 
set  at  defiance,  that  the  true  student  of  Nature  is  most 
hopeful  of  gaining  instruction.  The  observation  is 
very  startling,  it  is  true ;  and  the  explanation  may  be 
expected  to  be  also  surprising.  But  I  think  it  is  not 
far  to  seek.  The  satellite  cannot  have  retraced  its 
course;  Jupiter  cannot  have  shifted  his  place;  our 
atmosphere  cannot  be  in  question:  surely,  when  all 
these  explanations  are  eliminated,  our  task  is  rendered 


g  PREFACE. 

easier  instead  of  more  difficult.  A  change  of  shape  in 
Jupiter,  corresponding  to  that  which  I  have  endeav- 
ored to  exhibit  as  explaining  Saturn's  occasional  as- 
sumption of  the  square-shouldered  aspect,  would  obvi- 
ously account  for  the  .phenomenon.  "We  know  that 
Schroter  suspected  an  apparent  flattening  of  portions 
of  Jupiter's  outline.  Here  we  have  an  effective  con- 
firmation of  that  long-doubted  observation.  If  we 
consider  the  matter  rightly,  the  observation  made 
simultaneously  by  Smyth,  Maclear,  and  Pearson, 
makes  that  view  all  but  certain,  which  in  the  text  I 
have  presented  only  as  a  highly-probable  hypothesis. 

In  preparing  the  Maps  for  my  new  Atlas  (now 
nearly  ready),  I  have  detected  signs  of  systematic  ag- 
gregation among  stars  visible  to  the  naked  eye,  which 
seem  to  me  to  place  beyond  all  question  the  fact  that 
Sir  William  Herschel  adopted  an  erroneous  hypothesis 
as  the  basis  of  his  system  of  star-gauging.  The  fact 
that  about  one-third  of  the  lucid  stars  are  collected  in 
a  region  having  the  greater  Magellanic  Cloud  nearly 
in  its  centre,  and  covering  less  than  one-sixth  of  the 
heavens,  has  never  yet,  so  far  as  I  am  aware,  been 
noticed.  Supplemented  by  other  facts  detected  during 
the  work  of  transferring  the  stars  of  the  British  As- 
sociation Catalogue  to  my  Maps,  the  existence  of  this 
rich  region  around  the  Nubeculae  disposes  at  once  of 


PREFACE.  9 

the  hypothesis  of  a  generally  uniform  distribution 
within  the  sidereal  system.  I  shall  be  enabled,  by 
Mr.  Brothers's  kindness,  to  illustrate  my  Lecture  on 
the  Stars  at  the  Royal  Institution  on  May  6th  by 
means  of  photographs  of  the  Maps  which  thus  con- 
clusively (at  least  in  my  opinion)  establish  the  theory 
that  there  exist  special  and  discernible  laws  of  aggre- 
gation among  the  lucid  stars. 

I  may  add  in  this  place  that  it  is  not  the  case,  as 
has  been  recently  asserted,  that  my  theories  respect- 
ing the  sidereal  system  have  been  founded  on  the 
discovery  that  certain  nebulae  are  gaseous.  That  dis- 
covery, so  far  from  being  opposed  to  the  theories  of 
Sir  William  Herschel,  afforded  most  striking  evidence 
of  his  wonderful  reasoning  powers,  since  he  had  been 
led  to  express  his  firm  conviction  that  many  nebulae 
are  gaseous,  had  confidently  asserted  that  the  Orion 
nebula  is  so,  and  had  even  anticipated  the  discovery 
of  the  variability  of  the  irregular  nebulae,  recently 
effected  by  Le  Sueur  of  Melbourne. 

My  theory  respecting  the  sidereal  system  has  been 
based  on  the  signs  of  systematic  aggregation  among 
the  lucid  stars,  and  of  a  more  intimate  association  of 
those  stars  with  the  Milky  Way  than  could  be  ex- 
pected were  Sir  William  Herschel's  fundamental 
theory  correct.  My  first  paper  on  the  subject,  in  the 


10  PREFACE. 

Intellectual  Observer  for  August,  1867,  was  entitled 
"  Notes  on  Star-Streams ; "  and  it  was  only  while 
inquiring  into  the  nature  of  stellar  aggregation  that 
I  was  led  to  notice  the  laws  of  nebular  distribution, 
and  so  to  inquire  into  the  relations  between  stars  and 
nebulae.  I  take  this  opportunity  of  thanking  my  kind 
friend,  the  editor  of  the  Intellectual  Observer  and 
Student,  for  the  exceptional  liberality  with  which 
he  has  found  a  place  for  views  professedly  opposed 
to  generally-received  opinions. 

The  theory  brought  forward  in  the  chapter  on 
Meteors  and  Comets  is  not  altogether  new.  The 
general  idea  on  which  it  is  grounded  has  been  dealt 
with  by  Mayer  and  Thompson,  while  the  relation  be- 
tween the  motions  of  discrete  bodies  and  the  forma- 
tion of  systems  of  orbs  has  been  dealt  with  by  Sir 
John  Herschel,  in  considering  his  father's  hypotheses 
respecting  the  nebulae.  That  idea,  however,  presented 
itself  independently  to  my  mind  when  I  was  writing 
my  treatise  on  Saturn  (at  which  time  my  acquaint- 
ance with  scientific  literature  was  very  limited  in- 
deed), and  is  definitely  stated  in  Note  B  of  the  Ap- 
pendix to  that  work.  The  line  of  reasoning  is  wholly 
new,  I  believe,  by  which  I  have  endeavored  to  show 
that  those  peculiarities  of  the  solar  system  which 
have  hitherto  been  regarded  as  affording  the  strongest 


PREFACE.  11 

objection  to  the  hypothesis  of  development,  may  be 
regarded  as  in  reality  the  direct  result  of  the  processes 
by  which  the  solar  system  has  reached  its  present  con- 
dition. In  the  preface  to  my  treatise  on  Saturn  I 
touched  on  the  possibility  that  some  such  explanation 
of  those  peculiarities  might  be  found,  remarking  that 
in  the  rings  of  Saturn  astronomers  may  one  day  rec- 
ognize the  action  of  the  processes  by  which  the  solar 
system  has  attained  its  present  state. 

In  the  chapter  on  the  Sun  I  have  entered  at  some 
length  into  the  subject  of  the  solar  corona,  partly  be- 
cause that  subject  is  full  of  interest  in  view  of  the 
approaching  total  solar  eclipse  visible  in  the  south  of 
Europe,  and  partly  because  I  have  seen  with  regret 
that  an  erroneous  theory  of  the  corona  has  been  re- 
cently promulgated,  which  seems  likely  at  the  present 
conjuncture  to  affect  mischievously  the  progress  of  re- 
search into  this  interesting  question  of  solar  physics. 
I  have  heard  with  much  pleasure  that  the  Astronomer 
Koyal,  at  the  last  meeting  of  the  Astronomical  Socie- 
ty, altogether  repudiated  any  share  in  starting  this 
theory.  Although  I  had  seen  his  name  associated 
with  it,  I  had  always  thought  it  incredible  that  a 
mathematician  so  skilful  and  clear- sighted  should  have 
advanced  or  adopted  so  ill-considered  an  hypothesis. 

I  tender  my  best  thanks  to  Mr.  Browning,  F.  R. 


12  PREFACE. 

A.  S.,  for  the  beautiful  colored  pictures  of  Jupiter  and 
Saturn,  which  illustrate  the  chapters  on  those  planets ; 
and  to  Mr.  Brothers,  F.  B,.  A.  S.,  for  his  careful  revi- 
sion of  the  proof-sheets,  and  the  detection  of  more  than 
one  error  which  had  escaped  my  scrutiny. 

EICHAKD  A.  PEOCTOB. 

LONDON,  April  12,  1870. 


CONTENTS. 


CHAP.  PAGE 

INTRODUCTION       .              .             .             .              .  .17 

I. — WHAT  THE  EARTH  TEACHES  us             .            .            .  22 

II. — WHAT  WE  LEARN  FROM  THE  SUN   .             .             .  .35 

III.— THE  INFERIOR  PLANETS             ....  71 

IV. MARS,   THE   MlNIATCRE   OF   OUR   EARTH          .  .  .97 

V.— JUPITER,  THE  GIANT  OF  THE  SOLAR  SYSTEM    .            .  123 

VI. — SATURN,  THE  RINGED  WORLD         ....  159 

VII. — URANUS  AND  NEPTUNE,  THE  ARCTIC  PLANETS  .            .  176 

VIII. — THE  MOON  AND  OTHER  SATELLITES            .            .  187 

IX.— METEORS  AND  COMETS  ;  THEIR  OFFICE  IN  THE  SOLAR  SYSTEM  202 

X. — OTHER  SUNS  THAN  OURS           .            .                        .  230 

XI.— OF  MINOR  STARS,  AND  OF  THE  DISTRIBUTION  OF  STARS  IN 

SPACE   .......  258 

XII. — THE  NEBULA,  ARE  THEY  EXTERNAL  GALAXIES  ?           .  282 
XIII.— SUPERVISION  AND  CONTROL             .            .            .            .805 


ILLUSTEATIOKS. 


THE  PLANET  JUPITER  (colored)          ....       Frontispiece. 
POUR  TELESCOPIC  DRAWINGS  OP  MARS  (colored)  to  face  p.  1(W 

CHART   OF    MARS,  ON   THE  STEREOGRAPHIC    PROJEC- 
TION (colored) to  face  p.  105 

THE  PLANET  JUPITER  (BROWNING) 


THE  PLANET  SATURN  (colored) 

THE  GALACTIC  CLOVEN  FLAT  RING  (plan) 

THE  GALACTIC  CLOVEN  FLAT  RING  (section)    . 

THE  GALACTIC  FLAT  RING,  MODIFIED  IN  ACCORDANCE 
WITH  THE  OBSERVED  PECULIARITIES  OF  THE 
MILKY  WAY 

THE  MILKY  WAY  REGARDED  AS  A  SPIRAL 

THE  PROPER  MOTIONS  OF  STARS  IN  GEMINI  AND  CAN- 
CER   

OBSERVED  PROPER  MOTIONS  OF  STARS  IN  URSA  MAJOR 
AND  NEIGHBORHOOD 


.    page  146 
to  face  p.  167 


page  264 
page  268 

page  278 
page  279 


OBSERVED   PROPER  MOTIONS    OF  STARS  IN   HEAD   OF 
ARIES 


THE  NEBULA,  MESSIER  17 


.   page  280 
to  face  p.  802 


OTHER  WORLDS  THAN  OURS. 


INTRODUCTION. 

ASTRONOMY  and  GEOLOGY  owe  much  of  their  charm 
tc  the  fact  that  they  suggest  thoughts  of  other  forms  of 
life  than  those  with  which  we  are  familiar.  Geology 
teaches  us  of  days  when  this  earth  was  peopled  with 
strange  creatures  such  as  now  are  not  found  upon  its 
surface.  We  turn  our  thoughts  to  the  epochs  when 
those  monsters  throve  and  multiplied,  and  picture  to 
ourselves  the  appearance  which  our  earth  then  pre- 
sented. Strange  forms  of  vegetation  clothe  the  scene 
which  the  mind's  eye  dwells  upon.  The  air  is  heavily 
laden  with  moisture  to  nourish  the  abundant  flora ; 
hideous  reptiles  crawl  over  their  slimy  domain,  battling 
with  each  other  or  with  the  denizens  of  the  forest ; 
huge  bat-like  creatures  sweep  through  the  dusky 
twilight  which  constituted  the  primeval  day ;  weird 
monsters  pursue  their  prey  amid  the  ocean-depths : 
and  we  forget,  as  we  dwell  upon  the  strange  forms 
which  existed  in  those  long-past  ages,  that  the  scene 
now  presented  by  the  earth  is  no  less  wonderful,  and 


18  OTHER    WORLDS  THAN  OURS. 

that  the  records  of  our  time  may  perhaps  seem  one  day 
as  perplexing  as  we  now  find  those  of  the  geological 
eras. 

Astronomy  has  a  kindred  charm.  We  cannot  in- 
deed examine  the  actual  substance  of  living  creatures 
existing  upon  other  celestial  bodies  ;  we  cannot  even 
picture  to  ourselves  their  appearance  or  qualities ;  and 
only  in  a  few  instances  can  we  even  form  any  con- 
ception of  the  conditions  under  which  they  live.  But 
we  see  proofs  on  all  sides  that,  besides  the  world  on 
which  we  live,  other  worlds  exist  as  well  cared  for  and 
as  nobly  planned.  Nay,  we  see  globes  by  the  side  of 
which  our  earth  would  seem  but  as  a  tiny  speck ;  we 
trace  these  globes  as  they  sweep  with  stately  motion 
on  their  appointed  courses ;  we  watch  the  return  of 
day  on  the  broad  expanse  of  their  surface ;  and  we  see 
systems  of  satellites  which  are  suspended  as  lights  for 
their  nocturnal  skies.  We  further  find  that  our  sun  is 
matched  by  a  thousand  thousand  suns  amid  the  im- 
measurable depths  of  space ;  and  the  mind's  eye  pic- 
tures other  worlds  like  those  which  course  around  the 
sun,  travelling  in  stately  orbits  around  his  fellow- 
luminaries. 

Long,  however,  before  the  wonders  of  modern  astron- 
omy had  been  revealed  to  us,  men  of  inquiring  minds 
seem  to  have  been  led,  as  by  an  irresistible  instinct,  to 
examine  into  the  resemblance  which  may  exist  between 
our  world  and  other  worlds  surrounding  it  on  every 
hand.  It  has  not  been  the  mere  fanciful  theorizer 
who  has  discussed  such  questions,  but  men  of  the 
highest  eminence  in  science.  In  long-past  ages  Anaxi- 


INTRODUCTION.  19 

maiider  and  Pythagoras  studied  tlie  subject  of  other 
worlds  than  ours;  later,  such  men  as  Huyghens, 
Galileo,  and  Newton,  have  dwelt  upon  the  same  in- 
teresting theme ;  while,  in  our  own  day,  Whewell  and 
Brewster  have  employed  their  scientific  and  dialectic 
skill  in  defending  rival  theories  upon  the  subject. 

Undoubtedly  a  large  share  of  the  interest  with 
which  the  question  of  other  worlds  than  ours  has  been 
regarded,  is  due  to  the  fact  that,  as  the  science  of  as- 
tronomy has  progressed,  the  subject  Eas  continually 
presented  itself  under  new  aspects.  The  question,  in 
fact,  is  one  of  those  which  are  ever  new  and  ever  old. 
It  has  all  the  charm  belonging  to  subjects  which  men 
in  all  ages  have  delighted  to  discuss,  while  it  is  asso- 
ciated in  the  most  intimate  manner  with  the  progress 
of  modern  science.  With  what  a  charm  of  novelty, 
for  instance,  the  discussion  between  Whewell  and 
Brewster  invested  the  subject!  No  doubt  a  large 
portion  of  that  charm  was  due  to  the  personal  qualities 
of  the  two  disputants.  Yet,  despite  the  skill  with 
which  each  of  them  presented  the  arguments  belong- 
ing to  his  own  side  of  the  controversy,  few  could  have 
read  with  any  interest  a  discussion  on  a  subject  BO 
well  worn,  had  it  not  been  that  the  arguments  were 
drawn  from  the  discoveries  which  had  recently  been 
made  by  astronomers.  Nor  was  it  uninteresting  to 
notice  how  these  discoveries  at  once  seemed  to  acquire 
a  new  interest  when  they  were  associated  with  the 
subject  of  life  in  other  worlds.  Facts  which  had 
attracted  little  notice  at  the  time  of  their  discovery,  at 
once  assumed  importance,  when  it  was  seen  how  they 


20  OTHER    WORLDS  THAN   OURS. 

bore  on  the  rival  views  which  Whewell  and  Brewster 
were  enforcing.  The  interest  with  which  the  public  re- 
gard many  of  these  discoveries  may,  indeed,  be  said  to 
date  from  the  controversy  between  those  eminent  men. 

No  very  long  interval,  if  we  count  by  years,  has 
elapsed  since  the  "  Plurality  of  Worlds  "  and  "  More 
Worlds  than  One  "  were  written.  Yet  so  rapidly  has 
science  progressed,  that  already  the  subject  of  life  in 
other  worlds  has  assumed  a  new  aspect.  Arguments 
which  were  hypothetical  thirty  years  ago  have  either 
become  certainties  or  been  disproved.  Doubtful  points 
have  been  cleared  up ;  a  new  meaning  has  been  found 
even  in  those  facts  which  were  well  known  to  both  the 
disputants ;  and  lastly,  a  new  mode  of  research  has 
been  devised,  which  has  not  only  revealed  a  number 
of  surprising  facts,  but  promises  to  work  yet  greater 
marvels  in  the  years  which  are  to  come. 

One  is  thus  invited  to  discuss  anew  a  subject  which 
but  a  few  years  since  seemed  thoroughly  sifted  by 
the  inquiries  of  the  two  eminent  philosophers  I  have 
named.  We  stand  in  a  position  much  more  favorable 
for  the  formation  of  just  views  than  that  from  which 
Whewell  and  Brewster  surveyed  the  planetary  and 
stellar  systems.  Never,  since  men  first  explored  the 
celestial  depths,  has  a  series  of  more  startling  dis- 
coveries rewarded  the  labors  of  astronomers  and 
physicists  than  during  the  past  few  years.  Unhoped- 
for revelations  have  been  made  on  every  side.  Anal 
ogies  the  most  interesting  have  brought  the  distant 
orbs  of  heaven  into  close  relationship  with  our  own 
earth,  or  with  the  central  luminary  of  the  planetary 


INTR  OD  UCTION-  2 1 

Bclieme.  And  a  lesson  lias  been  taught  us  which  bears 
even  more  significantly  on  our  views  respecting  the 
existence  of  other  worlds :  we  have  learned  to  recog- 
nize within  the  solar  system,  and  within  the  wondrous 
galaxy  of  which  our  sun  is  a  constituent  orb,  a  variety 
of  structure  and  a  complexity  of  detail,  of  which  but  a 
few  years  ago  astronomers  had  formed  but  the  most 
inadequate  conceptions. 

My  object,  then,  in  the  pages  which  follow,  is  not 
solely  to  establish  the  thesis  that  there  are  other  worlds 
than  ours,  but  to  present,  in  a  new  and  I  hope  interesting 
light,  the  marvellous  discoveries  which  have  rewarded 
recent  scientific  researches.  Judged  merely  according 
to  their  direct  significance,  these  discoveries  are  well 
calculated  to  excite  our  admiration  for  the  wonderful 
works  of  God  in  His  universe,  and  for  the  far-reaching 
scope  of  the  mental  powers  which  He  has  given  to  His 
creature  Man.  But  it  is  when  we  consider  recent 
discoveries  in  their  relation  to  the  existence  of  other 
worlds,  when  we  attempt  to  form  a  conception  of  the 
immense  varieties  of  the  forms  of  life  corresponding 
to  the  innumerable  varieties  of  cosmical  structure  dis- 
closed by  modern  researches,  that  we  recognize  the 
full  significance  of  those  discoveries.  Although  the 
growth  of  our  knowledge  is  ever  accompanied  by  a 
proportional  growth  of  our  estimate  of  the  unknown 
we  seem  already  entitled  to  say  that  we  have 

Come  on  that  which  is,  and  caught 
The  deep  pulsations  of  the  world, 
JEonian  music,  measuring  out 
The  steps  of  time. 


CHAPTER  1. 

WHAT   OUR    EARTH   TEACHES    US. 

BEFORE  proceeding  to  consider  the  various  circum- 
stances under  which  the  worlds  or  systems  which 
surround  us  appear  to  subsist,  it  may  be  well  to 
inquire  how  far  we  have  reason  to  conclude,  from  the 
consideration  of  our  own  earth  and  its  inhabitants, 
that  the  Creator  has  designed  the  orbs  which  exist 
throughout  space  for  the  support  of  living  creatures. 

It  would  not  be  just  to  argue  directly  from  the  fact 
that  the  earth  is  inhabited  to  the  conclusion  that  the 
other  planets  are  inhabited  also,  nor  thence  to  the  con- 
clusion that  other  stars  have,  like  our  sun,  their  attend- 
ant worlds,  peopled  with  various  forms  of  life.  An 
analogy  founded  on  a  single  instance  has  no  logical 
force.  And  it  is  doubtful  whether  we  have  not,  in  the 
moon,  an  instance  which  would  as  effectually  serve  to 
support  a  directly  opposite  conclusion.  It  seems  all 
but  certain,  as  we  shall  presently  have  occasion  to 
show,  that  no  part  of  the  moon's  globe  is  inhabited  by 
living  creatures.  Certainly  she  is  inhabited  by  none 
which  bear  the  least  resemblance  to  those  existing  on 
our  earth.  Thus  it  might  fairly  be  urged  that,  since 


WHAT  OUR  EARTH  TEACHES  US. 


23 


one  of  the  two  orbs  respecting  which  we  know  most 
appears  to  be  uninhabited,  there  remains  no  probable 
argument  in  favor  of  the  view  that  other  orbs  besides 
our  earth  are  the  abode  of  living  creatures. 

Yet  the  earth  in  reality  supplies  an  argument  of 
great  force,  when  we  consider  the  evidence  she  presents 
in  another  light.  The  mere  fact  that  this  world  is  in- 
habited is,  as  we  have  seen,  little ;  but  we  shall  find 
that  the  way  in  which  life  is  distributed  over  the 
earth's  surface  is  full  of  significance. 

If  we  range  over  the  earth,  from  the  arctic  regions 
to  the  torrid  zone,  we  find  that  none  of  the  peculiarities 
which  mark  the  several  regions  of  our  globe  suffice  to 
banish  life  from  its  surface.  In  the  bitter  cold  within 
the  arctic  circles,  with  their  strange  alternations  of  long 
summer  days  and  long  winter  nights,  their  frozen  seas, 
perennial  ice,  and  scanty  vegetation,  life  flourishes  in  a 
hundred  various  forms.  On  the  other  hand,  the  torrid 
zone,  with  its  blazing  heat,  its  long-continued  droughts, 
its  strange  absence  of  true  seasonal  changes,  and  its 
trying  alternations  of  oppressive  calms  and  fiercely- 
raging  hurricanes,  nourishes  even  more  numerous 
and  more  various  forms  of  life  than  either  of  the  great 
temperate  zones.  Around  mountain-summits  as  in  the 
depths  of  the  most  secluded  valleys,  in  mid-ocean  as  in 
the  arid  desert,  in  the  air  as  beneath  the  surface  of  the 
earth,  we  find  a  myriad  forms  of  life. 

But  this  is  far  from  being  all.  Yarious  as  are  the 
physical  habitudes  which  we  encounter  as  we  travel 
over  the  surface  of  our  globe,  we  are  able  to  trace  the 
existence  of  other  varieties  even  more  remarkable. 


24 


OTHER    WORLDS  THAN  OURS. 


The  geologist  lias  been  able  to  turn  back  a  few  leaves 
of  the  earth's  past  history,  and,  though  the  pages  have 
been  defaced  and  mutilated  by  Time's  unsparing  hand, 
he  is  yet  able  to  read  in  them  of  many  strange  vicissi- 
tudes to  which  the  continents  and  oceans  of  our  globe 
have  been  exposed.  But,  far  back  as  he  can  trace  the 
earth's  history,  and  already  he  counts  her  age  by  mill- 
ions of  years,*  he  finds  no  evidence  of  an  epoch  when 
life  was  absent  from  her  surface.  Nay,  if  he  reads 
aright  the  mysterious  lesson  which  the  blurred  letters 
teach  him,  he  is  led  to  believe  that,  at  the  most  distant 
epoch  to  which  his  researches  have  extended,  there 
was  the  same  wonderful  variety  in  the  forms  of  life 
as  at  the  present  day.  He  can,  indeed,  find  the  scat- 
tered remains  of  only  a  few  of  those  old-world 
creatures ;  but  he  recognizes,  in  those  which  have  been 
preserved,  the  clearest  evidence  that  thousands  of 
others  must  have  existed  around  them.  He  knows 
that,  of  a  million  creatures  now  existing,  scarcely  one 
will  leave  to  future  ages  any  record  of  its  existence  ; 
he  sees  whole  races  vanishing  from  the  earth,  leaving 
no  trace  behind  them ;  and  he  is  thus  able  to  form  an 

*  The  results  of  the  recent  deep-sea  dredging  expeditions,  though 
they  have  an  obvious  bearing  on  the  question  of  the  relative  ages  of  the 
various  strata  of  our  earth,  do  not  appreciably  affect  our  estimate  of  the 
range  of  time  during  which  this  world  has  been  the  abode  of  living 
creatures.  We  can  no  longer  assume  that  adjacent  rocks  which  diifer  in 
character  are  necessarily  different  in  age :  but  we  have  enough  evidence, 
from  superimposed  strata,  to  prove  the  enormous  antiquity  of  the  earlier 
formations.  The  researches  of  Dr.  Carpenter  and  his  fellow-workers 
have  a  most  important  bearing,  however,  on  the  subject  of  the  present 
chapter,  and  supply  a  more  forceful  analogy,  perhaps,  than  any  dwelt  on 
in  the  text,  in  favor  of  the  view  that,  under  the  widest  varieties  of  con. 
dition,  Nature  may  be  most  prodigal  of  life. 


WHAT  OUR  EARTH  TEACHES   US  2^ 

estimate  of  the  enormous  extent  by  which  the  creatures 
and  races  of  which  he  can  learn  nothing  must  have  out- 
numbered those  whose  scattered  remains  attest  their 
former  existence  upon  the  earth. 

Here,  then,  we  have  analogies  which  there  is  no 
mistaking.  We  see  that  not  only  is  Nature  careful  to 
fill  all  available  space  with  living  forms,  but  that  no 
time  over  which  our  researches  extend  has  found  her 
less  prodigal  of  life.  We  see  that,  within  very  wide 
limits,  she  has  a  singular  power  of  adapting  living 
creatures  to  the  circumstances  which  surround  them. 
Nor  is  this  lesson  affected — like  the  general  lesson 
drawn  from  the  mere  fact  of  the  earth's  being  inhabited 
— by  any  thing  we  can  learn  from  the  aspect  of  our 
satellite.  For  the  arguments  against  the  presence  of 
living  creatures  on  the  moon  are  founded  on  the  evi- 
dence we  have  that  the  physical  habitudes  of  that  orb 
are  outside  the  limits — wide  as  they  seem  to  be — 
within  which  Nature  can  effect  the  adaptation  we  have 
spoken  of. 

In  fact,  if  we  consider  rightly,  the  argument  which 
has  been  drawn  from  the  moon's  presumed  unfitness  to 
be  the  abode  of  living  creatures  is  so  founded  on  ter- 
restrial analogies  as  to  leave  the  contrary  argument 
unaffected.  We  have  to  assume  that  the  argument 
drawn  from  the  analogy  of  the  earth  is  forceful  before 
we  can  form  any  opinion  at  all  respecting  the  moon's 
hfibitability.  And,  in  any  case,  no  argument  can  be 
drawn  from  the  moon's  unfitness  for  the  support  of 
life,  against  the  view  that,  where  orbs  fit  for  the  sup- 
port of  life  exist,  there  Nature  has  provided  sucb 


26  OTHER    WORLDS  THAN  OURS. 

classes  of  living  creatures  as  are  adapted  to  the  special 
habitudes  of  those  orbs. 

The  moon  teaches  us,  however,  that  the  Creator 
has  not  intended  all  the  celestial  bodies  to  be  at  all. 
times  habitable.  The  sun  also  teaches  the  same  lesson. 
And  it  is  necessary  that  we  should  consider  how  far 
the  evidence  presented  by  our  own  earth  may  serve  to 
elucidate  this  teaching.  "We  shall  see,  as  we  proceed, 
that  terrestrial  analogies  afford  a  very  sure  guide  in 
the  midst  of  many  perplexities  which  the  study  of  the 
worlds  around  us  presents  to  our  contemplation. 

Let  us  trace  out  the  various  degrees  of  fitness  or 
unfitness  for  the  support  of  particular  forms  of  life, 
which  we  recognize  in  various  regions  of  our  earth. 

Often,  where  there  exists  so  slight  a  difference  be- 
tween two  regions  of  the  earth  that,  to  ordinary  obser- 
vation, it  would  appear  that  the  forms  of  life  existing  in 
one  should  be  well  adapted  to  the  other  also,  we  yet 
find  that  this  is  not  the  case.  Some  minute  peculiarity 
of  soil,  or  climate,  or  vegetation,  will  render  one  region 
absolutely  uniiAitbitable  by  a  race  which  lives  and 
thrives  in  the  other.  Darwin'  mentions  several  -in- 
stances in  which  an  apparently  insignificant  change  in 
the  circumstances  under  which  a  particular  race  has 
thriven,  and  sometimes  a  change  which  does  not,  at 
first  sight,  appear  to  be  in  the  least  connected  with  the 
well-being  of  the  race,  has  led  to  its  gradual  disappear 
ance.  And  it  seems  demonstrated  that  even  the  slow 
processes  of  change  to  which  every  part  of  the  earth 
is  subjected  would  suffice  to  destroy  a  number  of  the 
races  now  subsisting  on  its  surface,  were  the  character- 


WHAT  OUR  EARTH  TEACHES  US.  2J 

istics  of  those  races  unalterable.  But,  as  the  physical 
habitudes  of  their  abode  slowly  change,  the  various 
races  of  living  creatures  slowly  change  also,  so  as  to 
adapt  themselves  continually  to  the  varying  circum- 
stances under  which  they  live. 

The  lesson  taught  us  by  this  peculiarity  is  very- 
obvious.  On  the  one  hand,  we  see  that  it  would  be  by 
no  means  sufficient  to  indicate  a  general  resemblance 
between  the  physical  habitudes  of  our  earth  and  those 
of  some  far-distant  planet,  in  order  to  prove  that  that 
planet  is  the  abode  of  living  creatures  resembling  those 
on  our  own  earth.  But,  on  the  other  hand,  we  are 
taught  that  the  existence  of  differences  sufficient  to 
render  a  distant  planet  an  unsuitable  abode  for  such 
creatures  as  we  are  familiar  with,  cannot  force  upon  us 
the  conclusion  that  the  planet  is  uninhabited.  On  the 
contrary,  the  circumstance  we  have  been  considering 
teaches  us,  that  such  differences  as  would  suffice  to 
banish  life  of  certain  kinds  are  insufficient  to  banish 
life  of  all  kinds,  or  even  to  render  less  abundant  the 
forms  of  life  which  exist  under  those  changed  condi- 
tions. 

And  now  we  may  proceed  a  step  farther.  On  our 
earth  we  find  differences  of  climate  and  of  physical 
habitudes  generally,  which  are  much  more  important 
than  those  hitherto  dealt  with.  "We  see  that  not  only 
would  certain  races  perish  in  the  long-run,  if  removed 
from  their  own  abode  to  other  parts  of  the  earth,  but 
that,  in  some  instances,  the  process  of  destruction  would 
be  very  rapid  indeed.  If  we  were  to  remove  the  polar 
bears  from  their  arctic  fastnesses  to  tropical,  or  even 


28  OTHER    WORLDS  THAN  OURS. 

to  the  warmer  parts  of  temperate  regions,  a  very  few 
years  would  see  the  end  of  the  whole  race.  The  races 
inhabiting  steppes  and  prairies  would  quickly  perish, 
if  removed  to  mountain-regions.  Those  accustomed 
to  a  moisture-laden  air  and  abundant  vegetation  would 
not  survive  long  if  removed  to  the  desert. 

In  some  races,  indeed,  we  find  a  power  of  enduring 
such  changes  which  very  far  exceeds  that  possessed  by 
other  races.  Those  creatures,  for  example,  which  man 
has  domesticated  seem  capable  of  enduring  a  variety 
of  climate  or  of  circumstances,  which  would  destroy 
the  seemingly  more  vigorous  races  which  have  not  been 
subdued  to  the  yoke  of  man.* 

Even  man  himself,  however,  though  he  possesses  in 
an  unrivalled  degree  the  power  of  enduring  in  safety 
the  most  complete  change  of  climate,  scene,  and  cir- 
cumstances, is  yet  limited,  in  a  certain  sense,  in  his 
power  of  migration.  The  Englishman,  for  example, 
can  endure  the  fiercest  heat  of  the  tropics  or  the  bit- 
terest cold  of  arctic  and  antarctic  regions.  But  he 
cannot  safely  attempt  to  found  true  colonies  in  every 
part  of  the  earth's  surface.  Our  countrymen  in  India 
must  send  their  children  to  be  reared  in  England,  if 
they  wish  them  to  grow  up  strong  and  vigorous. 
There  can  be  little  doubt  that  if  a  thousand  men  and 

*  Humboldt  tells  us  that  "  the  pliability  of  the  organization  of  those 
animals  which  man  has  subjected  to  his  sway,  enables  horses,  cows,  and 
other  species  of  European  origin,  to  lead  for  a  time  an  amphibious  life, 
surrounded  by  crocodiles,  water-serpents,  and  manatees.  When  the 
rivers  return  again  to  their  beds,  the  horses  roam  in  the  savannah, 
which  is  then  spread  over  with  a  fine  odoriferous  grass ;  and  enjoy,  as  in 
their  native  climate,  the  renewed  vegetation  of  spring." 


WHAT  OUR  EARTH  TEACHES   US.  2$ 

women  from  this  country  were  to  settle  in  certain  parts 
of  India  (not  at  any  time  intermarrying  with  the  na- 
tives), the  colony  would  have  disappeared  within  a 
couple  of  centuries. 

Here  we  have  a  second  degree  of  unfitness,  accord- 
ing to  which  certain  countries  would  quickly  become 
depopulated,  if  supplied  with  inhabitants  from  certain 
other  countries.  We  are  taught  the  same  lesson  as 
before,  but  in  a  more  striking  manner.  We  see  that 
differences  exist  within  the  confines  of  our  own  earth, 
which  render  particular  countries  absolutely  uninhab- 
itable by  particular  races,  insomuch  that,  though  the 
individual  might  survive,  the  race  itself  would  quickly 
perish.  And  we  see,  on  the  other  hand,  that  these 
countries  are  not  uninhabited,  or  even  less  fully  peo- 
pled with  living  creatures,  than  seemingly  more  fortu- 
nate abodes. 

Now,  if  some  impassable  barrier  prevented  the  in- 
habitants of  one  country  from  visiting  others,  while 
yet  it  was  possible  to  learn  something  of  the  conditions 
prevailing  in  other  regions,  how  readily  the  conclusion 
might  be  reached,  that  some  at  least  of  those  inac- 
cessible regions  must  be  wholly  uninhabited,  simply 
because  their  physical  habitudes  appeared  unstiited 
to  the  wants  of  the  only  creatures  with  which  the 
observer  was  familiar.  Who  would  believe,  for-  ex- 
ample, that  men  can  live,  and  not  only  live  but  thrive 
and  multiply,  in  the  frost-bound  regions  within  the 
Arctic  circle,  if  travellers  had  not  visited  the  Esquimaux 
races,  and  witnessed  the  conditions  under  which  they 
subsist  ?  Again,  if  we  knew  nothing  of  India,  and 


3o  OTHER    WORLDS  THAN  OURS. 

some  one  pictured  to  us  the  intense  heat  of  the  Indian 
sun,  the  strange  alternations  of  weather  which  replace 
to  the  Indian  the  seasonal  changes  we  are  familiar 
with,  and  all  the  other  circumstances  which  render 
tropica.  regions  so  different  from  our  English  home, 
who  could  believe  that,  amid  those  seemingly  un- 
endurable vicissitudes,  there  are  races  of  men  that 
thrive  and  multiply,  even  as  our  people  in  their  tem- 
perate zone  ?  * 

Therefore,  in  examining  the  circumstances  of  other 
worlds  than  ours,  it  will  not  be  sufficient  to  prove  that 
certain  orbs  would  obviously  not  be  habitable  by  the 
races  subsisting  on  the  earth,  in  order  to  enforce  the 
conclusion  that  no  living  creatures  subsist  at  all  upon 
their  surface. 

Yet  another  step  farther,  however.  There  are 
regions  of  the  earth  where  the  individuals  of  races 
belonging  to  other  regions  quickly  perish.  The  air  of 
our  own  England  is  death  to  many  creatures.  And, 
indeed,  there  is  not  a  spot  in  the  whole  world  which 
would  not  be  fatal  in  a  brief  space  to  many  animals  and 
plants  belonging  to  other  regions.  Yet  each  spot, 
though  thus  fatal  to  certain  races,  is  inhabited  by 
numbers  of  others,  which  live  and  thrive  upon  its  sur- 
face. 

*  Perhaps  the  most  striking  instance  of  man's  power  of  living  under 
circumstances  seemingly  the  most  unfavorable,  is  to  be  found  in  the 
fact  that,  though  the  strongest  traveller  is  affected  seriously  by  the  rar- 
ity of  the  air  at  great  elevations,  yet  races  of  men  live  and  thrive  in 
Potosi,  Bogota,  and  Quito,  and — to  use  the  words  of  a  modern  writer — 
that  bull-fights  should  be  possible  at  an  elevation  at  which  Saussure 
hardly  had  energy  to  consult  his  instruments,  and  where  even  his  guides 
fainted  as  they  tried  to  dig  a  small  hole  in  the  snow, 


WHAT  OUR  EARTH  TEACHES  US.  ^L 

Here,  then,  is  our  third  lesson.  We  are  taught,  by 
the  analogy  of  our  earth,  that  it  is  not  even  sufficient 
to  show  that  a  planet  would  be  an  abode  quickly  fatal 
to  all  the  living  creatures  subsisting  on  our  globe,  to 
prove  that  it  is  therefore  uninhabited. 

But  we  have  yet  a  stronger  argument  to  touch  on. 
There  are  regions  of  our  earth  to  which  creatures  from 
other  regions  cannot  be  removed  without  being  imme- 
diately killed.  The  warm-blooded  animal  perishes,  if 
placed  for  a  brief  space  under  water.  The  fish  perishes, 
if  placed  for  a  brief  space  on  the  earth.*  What  could 
be  more  wonderful  to  us,  were  we  not  familiar  with 
the  fact,  than  that  there  are  living  creatures  within  the 
depths  of  that  ocean,  beneath  whose  surface  we  our- 
selves, and  the  land  creatures  we  are  familiar  with, 
cannot  remain  alive  many  minutes  ?  If  fishes  could 
reason,  how  could  they  believe  that  creatures  can  live 
in  comfort  in  that  element  which  is  death  to  them  ? 
Yet  land  and  river  and  sea  are  alike  peopled  with 
living  creatures,  each  race  as  well  adapted  as  its 
fellows  to  the  circumstances  in  which  it  is  placed. 

We  are  taught,  then,  yet  another  lesson.  We  see 
that,  even  though  we  could  prove  that  every  living 
creature  on  this  earth  would  at  once  perish  if  removed 
to  another  orb,  yet  we  cannot  thence  conclude  that 
that  orb  is  uninhabited.  On  the  contrary,  the  lesson 
conveyed  by  our  earth's  analogy  leads  to  the  conclusion 


*  Perhaps  the  fact  that  there  are  certain  kinds  of  fish  which  cannot 
only  live  out  of  water,  but  can  travel  across  the  dry  land,  or  climb  trees, 
affords  an  even  more  striking  instance  of  Nature's  power  of  adapting 
creatures  to  the  circumstances  which  surround  them. 


5 2  OTHER    WORLDS  THAN  OURS 

that  many  worlds  may  exist,  abundantly  supplied  with 
living  creatures  of  many  different  species,  where  yet 
every  form  of  life  upon  our  earth — bird,  beast,  or  fish, 
reptile,  insect,  or  animalcule — would  perish  in  a  few 
moments.* 

There  remains  yet  a  last  lesson  to  be  drawn  from 
terrestrial  analogies.  On  the  earth  there  are  regions 
where  no  form  of  life  exists  or  can  exist.  Within  the 
naming  crater  of  the  volcano,  or  in  the  frozen  heart  of 
the  iceberg,  no  living  creature  has  its  being.  Yet  even 
here  Nature  proves  to  us  that  the  great  end  and  aim 
of  all  her  working  is  to  afford  scope  and  room  for  new 
forms  of  life,  or  to  supply  the  wants  of  those  which 
already  exist.  The  volcano  will  die  out,  and  the 
scene  of  its  activity  will  one  day  become  the  abode  of 
myriads  of  living  creatures  who  would  have  perished 
in  a  moment  in  its  consuming  fires.  The  iceberg  will 
melt,  and  its  substance  will  once  again  be  peopled  with 
busy  life.  But  this  is  little.  It  is  the  work  of  which 

*  I  might  add,  to  the  instances  here  cited,  many  others  which  seem 
even  more  striking.  I  have  already  referred  to  Dr.  Carpenter's  dis- 
covery, that  in  the  depths  of  the  Atlantic,  where  the  pressure  of  the  sea 
is  so  enormous  that  no  ordinary  instruments  can  resist  its  effects,  where 
it  had  even  been  thought  that  no  light  can  penetrate,  there  are  myriads 
of  living  creatures  having  even  organs  of  vision.  We  know,  too,  that  in 
strong  acids  which  would  instantly  kill  bird,  beast,  fish,  or  insect  placed 
within  them,  there  exist  and  thrive  minute  creatures,  adapted  by  Nature 
to  the  strange  conditions  ha  which  they  are  placed.  Even  in  the  bowels  of 
the  earth  and  in  the  very  neighborhood  of  active  volcanoes,  we  find  the 
volcano-fish  existing  in  such  countless  thousands,  that,  when  they  are 
from  time  to  time  vomited  forth  by  the  erupting  mountain,  their  bodies 
are  strewn  over  enormous  regions,  and,  as  they  putrefy  beneath  the  sun's 
rays,  spread  pestilence  and  disease  among  the  inhabitants  of  the  neigh- 
boring districts. 


WHAT  OUR  EARTH  TEACHES  US.  33 

volcano  and  iceberg  are  the  signs,  which  most  signifi- 
cantly teaches  us  what  is  Nature's  real  aim.  The 
volcano  is  the  index  of  those  busy  subterranean  forces 
which  are  remodelling  the  earth's  frame,  slowly  chan- 
ging the  level  of  the  land,  making  continents  of  oceans 
and  oceans  of  continents,  preserving  and  vivifying  all 
things,  while  all  things  seem  to  suffer  a  gradual  de- 
struction. The  iceberg,  too,  has  its  work  in  remod- 
elling and  fashioning  the  surface  of  new  continents. 
But  it  exhibits  also  the  action  of  Nature  for  the  present 
benefit  of  the  creatures  which  exist  upon  the  earth. 
It  acts  an  important  part  in  the  formation  and  main- 
tenance of  the  system  of  oceanic  circulation  on  which 
the  welfare  of  land  creatures  and  water  creatures  so 
largely  depends.  And  so  of  a  multitude  of  other 
phenomena,  which  appear  at  first  sight  significant 
rather  of  the  destructive  than  of  the  life-preserving 
character  of  Nature.  The  tornado  and  the  thunder- 
storm, the  earthquake  and  the  volcano — nay,  even  the 
dreaded  returns  of  plague  and  pestilence,  have  each  a 
more  powerful  influence  by  far  toward  the  preservation 
than  they  have  toward  the  destruction  of  life. 

We  see,  then,  that  even  when  we  can  prove  that  an 
orb  in  space  is  so  circumstanced  that  no  life  could  by 
any  possibility  exist  upon  its  surface;  if  it  were  the 
scene  of  a  fierce  and  destructive  turmoil,  one  moment 
of  which  would  suffice  to  destroy  every  living  creature 
now  existing  upon  the  earth ;  if  its  whole  mass  were 
heated  to  a  degree  a  thousandfold  more  intense  than 
that  of  the  fiercest  heat  we  know  of;  if  its  surface  were 
bound  in  a  cold  compared  with  which  our  arctic  frosts 


34  OTHER   WORLDS  THAN  OURS. 

would  seem  like  tropical  heat ;  or  even  if  the  most  rapid 
alternation  of  these  extremes  took  place  upon  and 
within  it ,-  even  then  we  could  not  conclude  that  the 
principal  purpose  for  which  the  Almighty  had  created 
it  had  not  been  the  support  of  life,  either  in  long-past 
ages,  or  in  ages  yet  to  come.  And  lastly,  though  we 
could  safely  assert  of  any  celestial  object,  that  neither 
now,  nor  at  any  past  or  future  time,  could  it  serve  as 
the  abode  of  living  creatures,  yet  we'  are  led  by 
terrestrial  analogies  to  the  conclusion  that  it  has  yet 
been  created  to  support  life  in  other  ways.  So  that 
those  very  orbs,  of  which  it  seems  safest  to  assert  that 
they  are,  have  ever  been,  and  must  ever  remain  un- 
inhabited, speak  to  us,  no  less  strongly  than  those 
which  appear  best  suited  for  habitation,  of  the  exist- 
ence of  other  worlds  than  ours. 


CHAPTER  II. 

WHAT   WE   LEABN   FROM   TUB   SUN. 

I  DO  not  propose  to  dwell  in  this  chapter  on  the  views 
which  have  been  propounded  respecting  the  sun's 
habitability.  It  is  not  merely  that  I  regard  those 
views  as  too  biza/rre  and  fanciful  to  find  place  in  a 
serious  consideration  of  the  subject  I  am  dealing  with, 
nor  that  the  progress  of  recent  observation  has  rendered 
them  utterly  untenable,  but  that,  in  fact,  they  do  not 
belong  to  what  the  sun  teaches  us.  I  wish  to  consider 
only  the  real  evidence  which  the  sun  affords  respecting 
the  scheme  of  creation,  to  dwell  upon  the  purposes 
which  he  subserves  in  the  economy  of  the  solar  system, 
and  thence  to  deduce  a  lesson  respecting  those  other 
suns  scattered  throughout  space,  which  we  call  the 
fixed  stars. 

Let  us  first  endeavor  to  form  adequate  conceptions 
respecting  the  dimensions  of  the  great  central  luminary 
of  the  solar  system. 

Let  the  reader  consider  a  terrestrial  globe  three 
inches  in  diameter,  and  search  out  on  that  globe  the 
tiny  triangular  speck  which  represents  Great  Britain. 
Then  let  him  endeavor  to  picture  the  town  in  which 


j  6         OTHER  WORLDS  THAN  OURS. 

he  lives  as  represented  by  the  minutest  pin-mark  that 
could  possibly  be  made  upon  this  speck.  He  will  then 
have  formed  some  conception,  though  but  an  inade- 
quate one,  of  the  enormous  dimensions  of  the  earth's 
globe,  compared  with  the  scene  in  which  his  daily  life 
is  cast.  Now,  on  the  same  scale,  the  sun  would  be  rep- 
resented by  a  globe  about  twice  the  height  of  an  ordi- 
nary sitting-room.  A  room  about  twenty-six  feet  in 
length,  and  height,  and  breadth,  would  be  required  to 
contain  the  representation  of  the  sun's  globe  on  this 
Bcale,  while  the  globe  representing  the  earth  could  be 
placed  in  a  moderately  large  goblet. 

Such  is  the  body  which  sways  the  motions  of  the 
solar  system.  The  largest  of  his  family,  the  giant 
Jupiter,  though  of  dimensions  which  dwarf  those  of  the 
earth  or  Yenus  almost  to  nothingness,  would  yet  only 
be  represented  by  a  thirty-two  inch  globe,  on  the  scale 
which  gives  to  the  sun  the  enormous  volume  I  have 
spoken  of.  Saturn  would  have  a  diameter  of  about 
twenty-eight  inches,  his  ring  measuring  about  five  feet 
in  its  extreme  span.  Uranus  and  Neptune  would  be 
little  more  than  a  foot  in  diameter,  and  all  the  minor 
planets  would  be  less  than  the  three-inch  earth.  It 
will  thus  be  seen  that  the  sun  is  a  worthy  centre  of  the 
great  scheme  he  sways,  even  when  we  merely  regard 
his  dimensions. 

The  sun  outweighs  fully  seven  hundred  and  forty 
times  the  combined  mass  of  all  the  planets  which 
circle  around  him,  so  that,  when  we  regard  the  energy 
of  his  attraction,  we  still  find  him  a  worthy  ruler  of 
the  planetary  scheme. 


WHAT   WE  LEARN  FROM  THE  SUN. 


37 


But,  after  all,  the  enormous  volume  and  mass  of 
the  sun  form  the  least  important  of  his  characteristics 
as  the  ruling  body  of  the  solar  system.  It  is  when  we 
contemplate  him  as  the  source  whence  the  supplies 
of  heat  and  light  required  by  our  own  world  and  the 
other  planets  are  plentifully  bestowed,  that  we  see 
what  is  his  chief  office  in  the  economy  of  the  planetary 
scheme. 

Properly  speaking,  the  physical  constitution  of  the 
eun  only  requires  to  be  dealt  with  in  such  a  work  as 
the  present  in  so  far  as  it  is  directly  associated  with 
the  sun's  action  upon  the  worlds  around  him,  or  as  it 
may  bear  on  the  question  of  the  constitution  of  those 
worlds.  But  the  subject  is  so  interesting,  and  it  would 
indeed  be  so  difficult  to  draw  a  line  of  demarcation 
between  the  facts  which  bear  upon  the  question  of 
other  worlds  and  those  which  do  not,  that  I  may  be 
permitted  to  enter  at  some  length  into  a  consideration 
of  the  solar  orb,  as  modern  physical  discoveries  pre- 
sent it  to  our  contemplation. 

The  study  of  solar  physics  may  be  said  to  have 
commenced  with  the  discovery  of  the  sun-spots,  about 
two  hundred  and  sixty  years  ago.  These  spots  were 
presently  found  to  traverse  the  solar  disk  in  such  a 
way  as  to  indicate  that  the  sun  turns  upon  an  axis 
once  in  about  twenty-six  days.  Nor  will  this  rotation 
appear  slow,  when  we  remember  that  it  implies  a  mo- 
tion of  the  equatorial  parts  of  the  sun's  surface  at  a 
rate  exceeding  some  seventy  times  the  motion  of  our 
swiftest  express  trains. 

Next  came  the  discovery  that  the  solar  spots  are  not 


38  OTHER   WORLDS  THAN  OURS. 

Burface-stains,  but  deep  cavities  in  the  solar  substance. 
The  changes  of  appearance  presented  by  the  spots  as 
they  traverse  the  solar  disk  led  Dr.  Wilson  to  form  this 
theory  so  far  back  as  1Y79 ;  but,  strangely  enough,  it  is 
only  in  comparatively  recent  times  that  the  hypothesis 
has  been  finally  established,  since  even  within  the  last 
ten  years  a  theory  was  put  forward  which  accounted 
satisfactorily  for  most  of  the  changes  of  appearance 
observed  in  the  spots,  by  supposing  them  to  be  due  to 
solar  clouds  hanging  suspended  at  a  considerable  ele- 
vation above  the  true  photosphere. 

Sir  "William  Herschel,  reasoning  from  terrestrial 
analogies,  was  led  to  look  on  the  spot-cavities  as  ap- 
ertures through  a  double  layer  of  clouds.  He  argued 
that,  were  the  solar  photosphere  of  any  other  nature,  it 
would  be  past  comprehension  that  vast  openings  should 
form  in  it,  to  remain  open  for  months  before  they  close 
up  again.  Whether  we  consider  the  enormous  rapidity 
with  which  the  spots  form  and  with  which  their  figure 
changes,  or  the  length  of  time  that  many  of  them  remain 
visible,  we  find  ourselves  alike  perplexed,  unless  we 
assume  that  the  solar  photosphere  resembles  a  bed  of 
clouds.  Through  a  stratum  of  terrestrial  clouds  open- 
ings may  be  formed  by  atmospheric  disturbances,  but 
while  undisturbed  the  clouds  will  retain  any  form  once 
impressed  upon  them,  for  a  length  of  time  correspond- 
ing to  the  weeks  and  months  during  which  the  solar 
spots  enduie. 

And  because  the  solar  spots  present  two  distinct 
varieties  of  light,  the  faint  penumbra  and  the  dark 
umbra  or  nucleus,  Herschel  saw  the  necessity  of  assum- 


WHAT   WE  LEARN  FROM  THE  SUN.  39 

ing  that  there  are  two  beds  of  clouds,  the  outer  self- 
luminous  and  constituting  the  true  solar  photosphere, 
the  inner  reflecting  the  light  received  from  the  outer 
layer,  and  so  shielding  the  real  surface  of  the  sun  from 
the  intense  light  and  heat  which  it  would  otherwise 
receive. 

But  while  recent  discoveries  have  confirmed  Sir 
William  Herschel's  theory  about  the  solar  cloud- 
envelopes,  they  have  by  no  means  given  countenance 
to  his  view  that  the  body  of  the  sun  may  possibly  be 
cool.  The  darkness  of  the  nucleus  of  a  spot  is  found, 
on  the  contrary,  to  give  proof  that  in  that  neighbor- 
hood the  sun  is  hotter,  because  it  parts  less  readily 
with  its  heat.  We  shall  see  presently  how  this  is. 
Meantime  let  it  be  noticed,  in  passing,  that  a  close 
scrutiny  of  large  solar  spots  has  revealed  the  existence 
of  an  intensely  black  spot  in  the  midst  of  the  umbra. 
This  black  spot  must  be  regarded  as  the  true  nucleus. 

The  circumstance  that  the  spots  appear  only  on  two 
bands  of  the  sun's  globe,  corresponding  to  the  sub- 
tropical zones  on  our  own  earth,  led  the  younger 
Herschel  to  conclusions  as  important  as  those  which 
his  father  had  formed.  He  reasoned,  like  his  father, 
from  terrestrial  analogies.  On  our  own  earth  the  sub- 
tropical zones  are  the  regions  where  the  great  cyclonic 
storms  have  their  birth,  and  rage  with  their  chief  fury. 
Here,  therefore,  we  have  the  analogue  of  the  solar 
spots,  if  only  we  can  show  reason  for  believing  that 
any  causes  resembling  those  which  generate  the 
terrestrial  cyclone  operate  upon  those  regions  of  the 
sun  where  the  solar  spots  make  their  appearance. 


4o 


OTHER    WORLDS  THAN  OURS. 


"We  know  that  the  cyclone  is  due  to  the  excess  of 
heat  at  the  earth's  equator.  It  is  true  that  this  ex- 
cess of  heat  is  always  in  operation,  whereas  cyclones 
are  not  perpetually  raging  in  sub-tropical  climates. 
Ordinarily,  therefore,  the  excess  of  heat  does  not 
cause  tornadoes.  Certain  aerial  currents  are  generated, 
whose  uniform  motion  suffices,  as  a  rule,  to  adjust  the 
conditions  which  the  excess  of  heat  at  the  equator 
would  otherwise  tend  to  disturb.  But  when  through 
any  cause  the  uniform  action  of  the  aerial  currents  is 
either  interfered  with,  or  is  insufficient  to  maintain 
equilibrium,  then  cyclonic  or  whirling  motions  are 
generated  in  the  disturbed  atmosphere,  and  propagated 
over  a  wide  area  of  the  earth's  surface. 

Now  we  recognize  the  reason  of  the  excess  of  heat 
at  the  earth's  equator,  in  the  fact  that  the  sun  shines 
more  directly  upon  that  part  of  the  earth  than  on  the 
zones  which  lie  in  higher  latitudes.  Can  we  find  any 
reason  for  suspecting  that  the  sun,  which  is  not  heated 
from  without  as  the  earth  is,  should  exhibit  a  similar 
peculiarity  ?  Sir  John  Herschel  considers  that  we 
can.  If  the  sun  has  an  atmosphere  extending  to  a 
considerable  distance  from  his  surface,  then  there  can 
be  little  doubt  that,  owing  to  his  rotation  upon  his 
axis,  this  atmosphere  would  assume  the  figure  of  an 
oblate  spheroid,  and  would  be  deepest  over  the  solar 
equator.  Here,  then,  more  of  the  sun's  heat  would 
be  retained  than  at  the  poles,  where  the  atmosphere 
is  shallowest.  Thus,  that  excess  of  heat  at  the  solar 
equator  which  is  necessary  to  complete  the  analogy 


WHAT   WE  LEARN  FROM  THE  SUN.  ^ 

between  the  sun-spots  and  terrestrial  cyclones,  seems 
satisfactorily  established. 

It  must  be  remarked,  however,  that  this  reasoning, 
so  far  as  the  excess  of  heat  at  the  sun's  equator  is  con- 
cerned, only  removes  the  difficulty  a  step.  If  there 
were  indeed  an  increased  depth  of  atmosphere  over  the 
sun's  equator  sufficing  to  retain  the  requisite  excess  of 
heat,  then  the  amount  of  heat  we  receive  from  the 
sun's  equatorial  regions  ought  to  be  appreciably  less 
than  the  amount  emitted  from  the  remaining  portions 
of  the  solar  surface.  This  is  not  found  to  be  the  case, 
so  that,  either  there  is  no  such  excess  of  absorption,  or 
else  the  solar  equator  gives  out  more  heat,  in  other 
words,  is  essentially  hotter,  than  the  rest  of  the  sun. 
But  this  is  just  the  peculiarity  of  which  we  want  the 
interpretation. 

It  may  be  taken  for  granted,  however,  that  there 
is  an  analogy  between  the  sun-spots  and  terrestrial 
cyclo/iic  storms,  though  as  yet  we  are  not  very  well 
able  to  understand  its  nature. 

Then  next  we  come  to  one  of  the  most  interesting 
discoveries  ever  made  respecting  the  sun — the  discovery 
that  the  spots  increase  and  diminish  in  frequency  in 
a  periodic  manner.  "We  owe  this  discovery  to  the 
laborious  and  systematic  observations  made  by  Herr 
Schwabe,  of  Dessau.  In  these  pages  any  account  of 
his  work  would  be  out  of  place.  We  need  only  dwell 
upon  the  result,  and  upon  other  discoveries  which  have 
been  made  by  observers  who  have  taken  up  the  same 
work. 

Schwabe  found  in  the  course  of  about  ten  and  a 


qz  OTHER    WORLDS   THAN  OURS. 

half  years,  the  solar  spots  pass  through  a  complete 
cycle  of  changes.  They  become  gradually  more  arid 
more  numerous  up  to  a  certain  maximum,  and  then 
as  gradually  diminish.  At  length  the  sun's  face  be- 
comes not  only  clear  of  spots,  but  a  certain  well- 
marked  darkening  around  the  border  of  his  disk  disap- 
pears altogether  for  a  brief  season.  At  this  time  the 
sun  presents  a  perfectly-uniform  disk.  Then  gradually 
the  spots  return,  become  more  and  more  numerous, 
and  so  the  cycle  of  changes  is  run  through  again. 

The  astronomers  who  have  watched  the  sun  from 
the  Kew  Observatory  have  found  that  the  process  of 
change  by  which  the  spots  sweep  in  a  sort  of  "  wave 
of  increase  "  over  the  solar  disk  is  marked  by  several 
minor  variations.  As  the  surface  of  a  great  sea-wave 
will  be  traversed  by  small  ripples,  so  the  gradual  in- 
crease and  diminution  in  the  number  of  the  solar  spots 
are  characterized  by  minor  gradations  of  change,  which 
are  sufficiently  well  marked  to  be  distinctly  cognizable. 

There  seems  every  reason  for  believing  that  the 
periodic  changes  thus  noticed  are  due  to  the  influence 
of  the  planets  upon  the  solar  photosphere,  though  in 
what  way  that  influence  is  exerted  is  not  at  present 
perfectly  clea,r.  Some  have  thought  that  the  mere 
attraction  of  the  planets  tends  to  produce  tides  of 
some  sort  in  the  solar  envelopes.  Then,  since  the 
height  of  a  tide  so  produced  varies  as  the  cube  or 
third  power  of  the  distance,  it  has  been  thought  that 
a  planet  when  in  perihelion  would  generate  a  much 
larger  solar  tide  than  when  in  aphelion.  So  that,  as 
Jupiter  has  a  period  nearly  equal  to  the  sun-spot  pe- 


WHAT   WE  LEARN  FROM  THE  SUN.  43 

riod,  it  has  been  supposed  that  the  attractions  of  this 
planet  are  sufficient  to  account  for  the  great  spot-pe- 
riod. Yenus,  Mercury,  the  Earth,  and  Saturn  have, 
in  a  similar  manner,  been  rendered  accountable  for 
the  shorter  and  less  distinctly  marked  periods. 

Without  denying  that  the  planets  may  be,  and  prob- 
ably are,  the  bodies  to  whose  influence  the  solar-spot 
periods  are  to  be  ascribed,  I  yet  venture  to  express 
very  strong  doubts  whether  the  attraction  of  Jupiter 
is  so  much  greater  in  perihelion  than  in  aphelion  as 
to  account  for  the  fact  that  whereas  at  one  season 
the  face  of  the  sun  shows  many  spots,  at  another  it  is 
wholly  free  from  them.* 

However,  we  are  not  at  present  concerned  so  much 
with  the  explanation  of  facts  as  with  the  facts  them- 
selves. We  have  to  consider  rather  what  the  sun  is 
and  what  he  does  for  the  solar  system,  than  why  these 
things  are  so. 

Let  us  note,  before  passing  to  other  circumstances 
of  interest  connected  with  the  sun,  that  the  variable 
condition  of  his  photosphere  must  cause  him  to  change 
in  brilliancy  as  seen  from  vast  distances.  If  Herr 
Schwabe,  for  instance,  instead  of  observing  the  sun's 
spots  from  his  watch-tower  at  Dessau,  could  have  re- 
moved himself  to  a  distance  so  enormous  that  the 
sun's  disk  would  have  been  reduced,  even  in  the  most 
powerful  telescope,  to  a  mere  point  of  light,  there  can 

*  Recently  Prof.  Kirkwood  has  published  a  most  interesting  series  of 
Inquiries,  going  far  to  prove  that  the  real  secret  of  the  planetary  influ- 
ences lies  in  the  fact  that  the  sun's  surface  is  not  uniform,  and  that 
on  a  certain  solar  longitude  the  planetary  influences  are  more  effective 
than  elsewhere. 


44 


OTHER  WORLDS  THAN  OURS. 


be  no  doubt  that  the  only  effect  which  he  would  have 
been  able  to  perceive  would  have  been  a  gradual  in- 
crease and  diminution  of  brightness,  having  a  period 
of  about  ten  and  a  half  years. 

Our  sun,  therefore,  viewed  from  the  neighbor- 
hood of  any  of  the  stars,  whence  undoubtedly  he  would 
simply  appear  as  one  among  many  fixed  stars,  would 
be  a  "  variable,"  having  a  period  of  ten  and  a  half 
years.  And  further,  if  an  observer,  viewing  the  sun 
from  so  enormous  a  distance,  had  the  means  of  very 
accurately  measuring  its  light,  he  would  undoubtedly 
discover  that,  while  the  chief  variation  of  the  sun  takes 
place  in  a  period  of  ten  and  a  half  years,  its  light  is 
subjected  to  minor  variations,  having  shorter  periods. 

The  discovery  that  the  periodic  changea  of  the 
sun's  appearance  are  associated  with  the  periodic 
changes  in  the  character  of  the  earth's  magnetism  is 
the  next  that  we  have  to  consider. 

It  had  long  been  noticed  that,  during  the  course 
of  a  single  day,  the  magnetic  needle  exhibits  a  minute 
change  of  direction,  taking  place  in  an  oscillatory 
manner.  And,  when  the  character  of  this  vibration 
came  to  be  carefully  examined,  it  was  found  to  corre- 
spond to  a  sort  of  effort  on  the  needle's  part  to  turn 
toward  the  sun.  For  example,  when  the  sun  is  on 
the  magnetic  meridian,  the  needle  has  its  mean  posi- 
tion. This  happens  twice  in  the  day,  once  when  the 
sun  is  above  the  horizon,  and  once  when  he  is  below  it. 
Again,  when  the  sun  is  midway  between  these  two 
positions — which  also  happens  twice  in  the  day — the 
needle  has  its  mean  position,  because  the  northern  and 


WHAT  WE  LEARN  FROM   THE  SUN. 


45 


the  southern  ends  make  equal  efforts  (so  to  speak)  to 
direct  themselves  toward  the  sun.  Four  times  in  the 
day,  then,  the  needle  has  its  mean  position,  or  is  di- 
rected toward  the  magnetic  meridian.  But,  when  the 
sun  is  not  in  one  of  the  four  positions?  considered,  that 
end  of  the  needle  which  is  nearest  to  him  is  slightly 
turned  away  from  its  mean  position,  toward  him. 
The  change  of  position  is  very  minute,  and  only  the 
exact  modes  of  observation  made  use  of  in  the  present 
age  would  have  sufficed  to  reveal  it.  There  it  is, 
however,  and  this  minute  and  seemingly  unimportant 
peculiarity  has  been  found  to  be  full  of  meaning. 

Had  science  merely  measured  this  minute  variation, 
the  work  would  have  given  striking  evidence  of  the 
exact  spirit  in  which  men  of  our  day  deal  with  natural 
phenomena.  But  science  was  to  do  much  more.  The 
variations  of  this  minute  variation  were  to  be  inquired 
into ;  their  period  was  to  be  searched  for ;  the  laws  by 
which  they  were  regulated  and  by  which  their  period 
might  perhaps  itself  be  rendered  variable,  were  to  be 
examined  ;  and,  finally,  their  relation  to  other  natural 
laws  was  to  be  sought  after.  That  Science  should  set 
herself  to  an  inquiry  so  delicate  and  so  difficult,  in  a 
spirit  so  exacting,  was  nothing  unusual.  It  is  thus  that 
all  the  great  discoveries  of  our  day  have  been  effected. 
But  it  is  well  that  the  reader  should  recognize  the 
careful  scrutiny  to  which  natural  phenomena  have 
been  subjected  before  the  great  laws  we  have  to  con- 
sider were  made  known.  It  is  thought  by  many,  who 
have  not  been  at  the  pains  to  examine  what  Science  is 
really  doing  in  our  day,  that  the  wonders  she  presents 


46 


OTHER    WORLDS  THAN  OURS. 


to  men's  contemplation,  the  "startling  revelations  which 
are  being  made  from  day  to  day,  are  merely  dreams 
and  fancies,  which  replace  indeed  the  dreams  and 
fancies  of  old  times,  but  have  no  worthier  claims  on 
our  belief.  Those  who  carefully  examine  the  history 
of  science  will  be  forced  to  adopt  a  very  different 
opinion. 

The  minute  vibrations  of  the  magnetic  needle,  thus 
carefully  watched — day  after  day,  month  after  month, 
year  after  year — were  found  to  exhibit  a  yet  more 
minute  oscillatory  change.  They  waxed  and  waned 
within  narrow  limits  of  variation,  but  yet  in  a  manner 
there  was  no  mistaking.  The  period  of  this  oscillatory 
change  was  not  to  be  determined,  however,  by  the  ob- 
servations of  a  few  years.*  Between  the  time  when 
the  diurnal  vibration  was  least  until  it  had  reached  its 
greatest  extent,  and  thence  returned  to  its  first  value, 
no  less  than  ten  and  a  half  years  elapsed,  and  a  much 
longer  time  passed  before  the  periodic  character  of  the 
change  was  satisfactorily  determined. 

The  reader  will  at  once  see  what  these  observations 
tend  to.  The  sun-spots  vary  in  frequency  within  a 
period  of  ten  and  a  half  years,  and  the  magnetic  diur- 
nal vibrations  vary  within  a  period  of  the  same  du- 
ration. It  might  seem  fanciful  to  associate  the  two 

*  The  reader  must  not  understand  that  the  account  here  given 
presents  in  any  sense  even  a  general  view  of  the  labors  of  those  who 
have  studied  the  earth's  magnetism.  I  touch  only  on  those  points  by 
which  the  association  between  the  earth's  magnetism  and  the  physical 
condition  of  the  sun  is  most  clearly  indicated ;  because  these  points 
alone  bear  on  the  subject  of  this  chapter.  How  they  do  so  will  appear 
further  on. 


WHAT   WE  LEARN  FROM  THE  SUN. 


47 


periodic  series  of  changes  together,  and  doubtless  when 
the  idea  first  occurred  to  Lament,  it  was  not  with  any 
great  expectation  of  finding  it  confirmed,  that  he  ex- 
amined the  evidence  bearing  on  the  point.  Judging 
from  known  facts,  we  may  see  reasons  for  such  an 
expectation  in  the  correspondence  of  the  needle's 
diurnal  vibration  with  the  sun's  apparent  motion,  and 
the  law  which  has  been  found  to  associate  the  annual 
variations  of  the  magnet's  power  with  the  sun's  dis- 
tance. But  undoubtedly  when  the  idea  occurred  to 
Lamont,  it  was  an  exceedingly  bold  one,  and  the 
ridicule  with  which  the  first  announcement  of  the  sup- 
posed law  was  received,  even  in  scientific  circles,  suf- 
fices to  show  how  unexpected  that  relation  was,  which 
is  now  so  thoroughly  established.  For  a  careful  com- 
parison between  the  two  periods  has  demonstrated  that 
they  agree  most  perfectly,  not  merely  in  length,  but 
maximum  for  maximum,  and  minimum  for  minimum. 
When  the  sun-spots  are  most  numerous,  then  the  daily 
vibration  of  the  magnet  is  most  extensive,  while,  when 
the  sun's  face  is  clear  of  spots,  the  needle  vibrates 
over  its  smallest  diurnal  arc. 

Then  the  intensity  of  the  magnetic  action  has  been 
found  to  depend  upon  solar  influences.  The  vibra- 
tions by  which  the  needle  indicates  the  progress  of 
those  strange  disturbances  of  the  terrestrial  magnetism 
which  are  known  as  magnetic  storms,  have  been  found 
not  merely  to  be  most  frequent  when  the  sun's  face 
is  most  spotted,  but  to  occur  simultaneously  with  the 
appearance  of  signs  of  disturbance  in  the  solar  pho- 
tosphere. For  instance,  during  the  autumn  of  1859, 


48  OTHER    WORLDS  THAN  OURS. 

the  eminent  solar  observer,  Carrington,  noticed  the 
apparition  of  a  bright  spot  upon  the  sun's  surface. 
The  light  of  this  spot  was  so  intense,  that  he  ima- 
gined the  dark  glass  which  protected  his  eye  had  been 
broken.  By  a  fortunate  coincidence,  another  observer, 
Mr.  Hodgson,  happened  to  be  watching  the  sun  at  the 
same  instant,  and  witnessed  the  same  remarkable 
appearance.  Now  it  was  found  that  the  self-register- 
ing magnetic  instruments  of  the  Kew  Observatory  had 
been  sharply  disturbed  at  the  instant  when  the  bright 
spot  was  seen.  And  afterward  it  was  learned  that  the 
phenomena  which  indicate  the  progress  of  a  magnet- 
ic storm  had  been  observed  in  many  places.  Tele- 
graphic communication  was  interrupted,  and,  in  some 
cases,  telegraphic  offices  were  set  on  fire ;  auroras 
appeared  both  in  the  northern  and  southern  hemi- 
sphere during  the  night  which  followed ;  and  the 
whole  frame  of  the  earth  seemed  to  thrill  responsively 
to  the  disturbance  which  had  affected  the  great  cen- 
tral luminary  of  the  solar  system. 

The  reader  will  now  see  why  I  have  discussed  re- 
lations which  hitherto  he  may  perhaps  have  thought 
very  little  connected  with  my  subject.  He  sees  that 
there  is  a  bond  of  sympathy  between  our  earth  and  the 
sun  ;  that  no  disturbance  can  affect  the  solar  photo- 
sphere, without  affecting  our  earth  to  a  greater  or  less 
degree.  But  if  our  earth,  then  also  the  other  planets. 
Mercury  and  Venus,  so  much  nearer  the  sun  than  we 
are,  surely  respond  even  more  swiftly  and  more  dis- 
tinctly to  the  solar  magnetic  influences.  But  beyond 
our  earth,  and  beyond  the  orbit  of  moonless  Mars,  the 


WHAT  WE  LEARN  FROM  THE  SUN.  45 

magnetic  impulses  speed  with  the  velocity  of  light. 
The  vast  globe  of  Jupiter  is  thrilled  from  pole  to  pole 
as  the  magnetic  wave  rolls  in  upon  it ;  then  Saturn 
feels  the  shock,  and  then  the  vast  distances  beyond 
which  lie  Uranus  and  Neptune  are  swept  by  the  ever- 
lessening  yet  ever-widening  disturbance-wave.  "Who 
shall  say  what  outer  planets  it  then  seeks  ?  or  who, 
looking  back  upon  the  course  over  which  it  has  trav- 
elled, shall  say  that  planets  alone  have  felt  its  effects  ? 
Meteoric  and  cometic  systems  have  been  visited  by  the 
great  magnetic  wave,  and  upon  the  dispersed  mem- 
bers of  the  one  and  the  subtle  structure  of  the  other 
effects  even  more  important  may  have  been  produced 
than  those  striking  phenomena  which  characterize  the 
progress  of  the  terrestrial  or  planetary  magnetic 
Btorms. 

"When  we  remember  that  what  is  true  of  a  rela- 
tively great  solar  disturbance,  such  as  the  one  wit- 
nessed by  Messrs.  Carrington  and  Hodgson,  is  true  also 
(however  different  in  degree)  of  the  magnetic  influ- 
ences which  the  sun  is  at  every  instant  exerting,  we 
see  that  a  new  and  most  important  bond  of  union  ex- 
ists between  the  members  of  the  solar  family.  The 
sun  not  only  sways  them  by  the  vast  attraction  of  his 
gravity,  not  only  illumines  them,  not  only  warms  them, 
but  he  pours  forth  on  all  his  subtle  yet  powerful  mag- 
netic influences.  A  new  analogy  between  the  mem- 
bers of  the  solar  system  is  thus  introduced,  to  reenforce 
those  other  analogies  which  have  been  held  so  strik- 
ingly to  indicate  that  the  ends  for  which  our  earth  has 
been  created  are  not  different  from  those  which  the 
3 


5° 


OTHER   WORLDS  THAN  OURS. 


Creator  had  in  view  when  He  planned  the  other  mem- 
bers of  the  solar  system.* 

And  now  we  pass  on  to  other  discoveries,  bearing  at 
once  and  with  equal  force  upon  the  relations  between 
the  various  members  of  the  solar  scheme  and  upon  the 
position  which  that  scheme  occupies  in  the  universe. 

Hitherto  we  have  been  considering  the  teachings  of 
the  telescope  ;  we  have  now  to  consider  what  we  have 
learned  by  means  of  an  instrument  of  yet  higher 
powers.  As  I  shall  have  to  refer  very  frequently, 
throughout  this  volume,  to  the  teachings  of  the  spec- 
troscope, it  will  be  well  that  I  should  briefly  describe 
what  it  is  that  this  instrument  really  effects.  Were  I 
Bimply  to  state  the  results  of  its  use,  without  describing 
its  real  character,  many  of  my  readers  would  be  dis- 
posed to  believe  that  astronomers  are  as  credulous  as 
in  reality  they  are  exacting  and  scrupulous,  where  new 
facts  and  observations  are  in  question. 

The  real  end  and  aim  of  the  telescope,  as  applied  by 
the  astronomer  to  the  examination  of  the  celestial  ob- 
jects, is  to  gather  together  the  light  which  streams  from 
each  luminous  point  throughout  space.  We  may  re- 
gard the  space  which  surrounds  us  on  every  side  as  an 

*  I  must  remark  here,  once  for  all,  that  in  speaking  of  the  plans  of 
i  he  Creator,  of  His  mode  of  working,  or  of  the  laws  which  He  has  estab- 
lished, I  by  no  means  intend  such  words  to  be  taken  literally.  For 
want  of  better,  such  words  as  these  must  be  employed  in  speaking  of  the 
relations  between  Almighty  God  and  His  universe.  But  in  truth  these 
relations  are  as  inconceivable  by  us  as  infinity  of  space  or  infinity  of 
time.  We  know  that  they  exist,  as  certainly  as  we  know  that  space  and 
time  are  both  infinite,  but  human  language  can  no  more  indicate  their 
nature  than  it  can  present  to  the  mind  an  adequate  picture  of  space  or 


WHAT  WE  LEARN  FROM  THE  SUN.  5l 

ocean  without  bounds  or  limits,  an  ocean  across  which 
there  are  ever  sweeping  waves  of  light,  either  emitted 
directly  from  the  various  bodies  subsisting  throughout 
space,  or  else  reflected  from  their  surfaces.  Other 
forms  of  wave  also  speed  across  those  limitless  depths 
in  all  directions,  but  the  light-waves  are  those  which 
at  present  concern  us.  Our  earth  is  as  a  minute 
island  placed  within  the  ocean  of  space,  and  to  the 
shores  of  this  tiny  isle  the  light-waves  bear  their  mes- 
sage from  the  orbs  which  lie  like  other  isles  amid  the 
fathomless  depths  around  us.  With  the  telescope  the 
astronomer  gathers  together  portions  of  light-waves 
which  else  would  have  travelled  in  diverging  directions. 
By  thus  intensifying  their  action,  he  enables  the  eye 
to  become  cognizant  gf  their  true  nature.  Precisely  as 
the  narrow  channels  around  our  shores  cause  the  tidal 
wave,  which  sweeps  across  the  open  ocean  in  almost 
insensible  undulations,  to  rise  and  fall  through  a  wide 
range  of  variation,  so  the  telescope  renders  sensible 
the  existence  of  light-waves  which  would  escape  the 
notice  of  the  unaided  eye. 

The  telescope,  then,  is  essentially  a  light-gatherer. 

The  spectroscope  is  used  for  another  purpose.  It 
might  be  called  the  light-sifter.  It  is  applied  by  the 
astronomer  to  analyze  the  light  which  comes  to  him 
from  beyond  the  ocean  of  space,  and  so  to  enable  him 
to  learn  the  character  of  the  orbs  from  which  that 
light  proceeds. 

The  principle  of  the  instrument  is  simple,  though 
the  appliances  by  which  its  full  powers  can  alone  be 
educed  are  somewhat  complicated. 


j;2  OTHER    WORLDS  THAN  OURS. 

A  ray  of  sunlight  falling  on  a  prism  of  glass  or 
crystal  does  not  emerge  unchanged  in  character.  Dif- 
ferent portions  of  the  ray  are  differently  bent,  so 
that  when  they  emerge  from  the  prism  they  no  longer 
travel  side  by  side  as  before.  The  violet  part  of  the 
light  is  bent  most,  the  red  least;  the  various  colors 
from  violet  through  blue,  green,  and  yellow,  to  red, 
being  bent  gradually  less  and  less. 

The  prism  then  sorts,  or  sifts,  the  light-waves. 

But  we  want  the  means  of  sifting  the  light-waves 
more  thoroughly.  The  reader  must  bear  with  me  while 
I  describe,  as  exactly  as  possible  in  the  brief  space 
available  to  me,  the  way  in  which  the  first  rough  work 
of  the  prism  has  been  modified  into  the  delicate  and 
significant  work  of  the  spectroscope.  It  is  well  worth 
while  to  form  clear  views  on  this  point,  because  so 
many  of  the  wonders  of  modern  science  are  associated 
with  spectroscopic  analysis. 

If,  through  a  small  round  hole  in  a  shutter,  light 
is  admitted  into  a  darkened  room,  and  a  prism  be 
placed  with  its  refracting  angle  downward  and  hori- 
zontal, a  vertical  spectrum,  having  its  violet  end  up- 
permost, will  be  formed  on  a  screen  suitably  placed  to 
receive  it. 

But  now  let  us  consider  what  this  spectrum  really  is. 
If  we  take  the  light-waves  corresponding  to  any  partic- 
ular color,  we  know,  from  optical  considerations,  that 
these  waves  emerge  from  the  prism  in  a  pencil  exactly 
resembling  in  shape  the  pencil  of  white  light  which  falls 
on  the  prism.  They  therefore  form  a  small  circular  or 
oval  image  on  their  own  proper  part  of  the  spectrum 


WHAT   WE  LEARN  FROM  THE  SUN.  53 

Hence  the  spectrum  is  in  reality  formed  of  a  multi- 
tude of  overlapping  images,  varying  in  color  from  vio- 
let to  red.  It  thus  appears  as  a  rainbow-tinted  streak, 
presenting  every  gradation  of  color  between  the  utmost 
limits  of  visibility  at  the  violet  and  red  extremities. 

If  we  had  a  square  aperture  to  admit  the  light,  we 
should  get  a  similar  result.  If  the  aperture  were  ob- 
long, there  would  still  be  overlapping  images ;  but  if 
the  length  of  the  oblong  were  horizontal,  then,  since 
each  image  would  also  be  a  horizontally-placed  oblong, 
the  overlapping  would  be  less  than  when  the  images 
were  square.  Suppose  we  diminish  the  overlapping  as 
much  as  possible ;  in  other  words,  suppose  we  make  the 
oblong  slit  as  narrow  as  possible  ?  Then,  unless  there 
were  in  reality  an  infinite  number  of  images  distributed 
all  along  the  spectrum  from  top  to  bottom,  the  images 
might  be  so  narrowed  as  not  to  overlap  ;  in  which  case, 
of  course,  there  would  be  horizontal  dark  spaces  or  gaps 
in  our  spectrum.  Or,  again,  if  we  failed  in  finding  gaps 
of  this  sort  by  simply  narrowing  the  aperture,  we  might 
lengthen  the  spectrum  by  increasing  the  refracting  an- 
gle of  the  prism,  or  by  using  several  prisms,  and  so  on. 

The  first  great  discovery  in  solar  physics,  by  means 
of  the  analysis  of  the  prism  (though  the  discovery  had 
little  meaning  at  the  time),  consisted  in  the  recognition 
of  the  fact  that,  by  means  of  such  devices  as  the  above, 
dark  gaps  or  cross-lines  can  be  seen  in  the  solar  spec- 
trum. In  other  words,  light- waves  of  the  various  gra- 
dations corresponding  to  all  the  tints  of  the  spectrum 
from  violet  to  red,  do  not  travel  to  us  from  the  great 
central  luminary  of  our  system.  Kemembering  that 


J4 


OTHER   WORLDS   THAN  OURS. 


the  effect  we  call  color  is  due  to  tlie  length  of  the  light- 
waves, the  effect  of  red  corresponding  to  light-waves 
of  the  greatest  length,  while  the  effect  of  violet  corre- 
sponds to  the  shortest  light-waves,  we  see  that  in  effect 
the  sun  sends  forth  to  the  worlds  which  circle  around 
him  light-waves  of  many  different  lengths,  but  not  of 
all.  Of  so  complex  and  interesting  a  nature  is  ordi- 
nary daylight. 

But  spectroscopists  sought  to  interpret  these  dark 
lines  in  the  solar  spectrum,  and  it  was  in  carrying  out 
this  inquiry — which  even  to  themselves  seemed  almost 
hopeless,  and  to  many  would  appear  an  utter  waste  of 
time — that  they  lighted  upon  the  noblest  method  of 
research  yet  revealed  to  man. 

They  examined  the  spectra  of  the  light  from  incan- 
descent substances  (white-hot  metals  and  the  like),  and 
found  that  in  these  spectra  there  are  no  dark  lines. 

They  examined  the  spectra  of  the  light  from  the 
stars,  and  found  that  these  spectra  are  crossed  by  dark 
lines  resembling  those  in  the  solar  spectrum,  but  dif- 
ferently arranged. 

They  tried  the  spectra  of  glowing  vapors,  and  they 
obtained  a  perplexing  result.  Instead  of  a  number  of 
dark  lines  across  a  rainbow-tinted  streak,  they  found 
bright  lines  of  various  color.  Some  gases  would  give 
a  few  such  lines,  others  many,  some  only  one  or  two. 

Then  they  tried  the  spectrum  of  the  electric  spark, 
and  they  found  here  also  a  series  of  bright  lines,  but 
not  always  the  same  series.  The  spectrum  varied  ac- 
cording to  the  substances  between  which  the  spark 
was  taken,  and  the  medium  through  which  it  passed. 


WHAT   WE  LEARN  FROM  THE  SUN.  55 

Lastly,  they  found  that  the  light  from  an  incan- 
descent solid  or  liquid,  when  shining  through  various 
vapors,  no  longer  gives  a  spectrum  without  dark  lines, 
but  that  the  dark  lines  which  then  appear  vary  in 
position,  according  to  the  nature  of  the  vapor  through 
which  the  light  has  passed. 

Here  were  a  number  of  strange  facts,  seemingly  too 
discordant  and  too  perplexing  to  admit  of  being  inter- 
preted. Yet  one  discovery  only  was  wanting  to  bring 
them  all  into  unison. 

In  1859,  Kirchhoff,  while  engaged  in  observing  the 
solar  spectrum,  lighted  on  the  discovery  that  a  certain 
double  dark  line,  which  had  already  been  found  to 
correspond  exactly  in  position  with  the  double  bright 
line  forming  the  spectrum  of  the  glowing  vapor  of 
sodium,  was  intensified,  when  the  light  of  the  sun  was 
allowed  to  pass  through  that  vapor.  This  at  once 
suggested  the  idea,  that  the  presence  of  this  dark  line 
(or  rather,  pair  of  dark  lines)  in  the  spectrum  of  the 
sun  is  due  to  the  existence  of  the  vapor  of  sodium  in 
the  solar  atmosphere,  and  that  this  vapor  has  the  power 
of  absorbing  the  same  order  of  light-waves  as  it  emits. 
It  would  of  course  follow  from  this,  that  the  other 
dark  lines  in  the  solar  spectrum  are  due  to  the  pres- 
ence of  other  absorbent  vapors  in  its  atmosphere,  and 
that  the  identity  of  these  would  admit  of  being  estab- 
ashed  in  the  same  way,  supposing  this  general  law  to 
hold,  that  a  vapor  emits  the  same  light-waves  that  it 
is  capable  of  absorbing. 

Kirchhoff  was  soon  able  to  confirm  his  views  by  a 
variety  of  experiments.  The  general  principles  to 


j6  OTHER   WORLDS  THAN  OURS. 

which  his  researches  led — in  other  words,  the  princi- 
ples which  form  the  basis  of  spectrum-analysis — are  as 
follows : 

1.  An  incandescent   solid   or  liquid  gives  a  con- 
tinuous spectrum. 

2.  A  glowing   vapor  gives   a   spectrum  of  white 
lines,  each  vapor  having  its  own  set  of  bright  lines, 
so  that,  from  the  appearance  of  a  bright-line  spectrum, 
one  can  tell  the  nature  of  the  vapor  or  vapors  whose 
light  forms  the  spectrum. 

3.  An  incandescent  solid  or  liquid  shining  through 
absorbent   vapors  gives  a    rainbow-tinted    spectrum 
crossed  by  dark  lines,  these   dark  lines   having   the 
same  position  as  the  bright  lines  belonging  to  the 
spectra  of  the  vapors;  so  that,  from  the  arrangement 
of  the  dark  lines  in  such  a  spectrum,  one  can  tell  the 
nature   of  the  vapor   or  vapors  which  surround  the 
source  of  light.* 

*  To  these  may  be  added  the  following  laws : 

4.  Light  reflected  from  any  opaque  body  gives  the  same  spectrum  as 
it  would  have  given  before  reflection. 

5.  But  if  the  opaque  body  be  surrounded  by  vapors,  the  dark  lines 
corresponding  to  these  vapors  make  their  appearance  in  the  spectrum 
with  a  distinctness  proportioned  to  the  extent  to  which  the  light  has 
penetrated  those  vapors  before  being  reflected  to  us. 

6.  If  the  reflecting  body  be  itself  luminous,  the  spectrum  belonging 
to  it  is  superadded  to  the  spectrum  belonging  to  the  reflected  light. 

7.  Glowing  vapors  surrounding  an  incandescent  source  of  light  may 
cause  bright  lines  or  dark  lines  to  appear  in  the  spectrum,  according  as 
they  are  more  or  less  heated ;  or  they  may  emit  just  so  much  light  as  to 
make  up  for  what  they  absorb,  hi  which  case  there  will  remain  no  trace 
of  their  presence. 

8.  The  electric  spark  presents  a  bright-line  spectrum,  compounded 
of  the  spectra  belonging  to  the  vapors  of  those  substances  between  which, 
and  of  those  through  which,  the  discharge  takes  place.     According  tc 


WHAT   WE  LEARN  FROM  THE  SUV. 


57 


The  application  of  the  new  method  of  research  to 
the  study  of  the  solar  spectrum  quickly  led  to  a  number 
of  most  interesting  discoveries.  It  was  found  thatt 
besides  sodium,  the  sun's  atmosphere  contains  the  va- 
pors of  iron,  calcium,  magnesium,  chromium,  and 
other  metals.  The  dark  lines  corresponding  to  these 
elements  appear  unmistakably  in  the  solar  spectrum. 
There  are  other  metals,  such  as  copper  and  zinc,  which 
seem  to  exist  in  the  sun,  though  some  of  the  corre- 
sponding dark  lines  have  not  yet  been  recognized.  As 
yet  it  has  not  been  proved  that  gold,  silver,  mercury, 
tin.  lead,  arsenic,  antimony,  or  aluminium,  exist  in 
the  sun — though  we  can  by  no  means  conclude,  nor 
indeed  is  it  at  all  probable,  that  they  are  absent  from 
his  substance.  The  dark  lines  belonging  to  hydrogen 
are  very  well  marked  indeed  in  the  solar  spectrum,  and, 
as  we  shall  see  presently,  the  study  of  these  lines  has 
afforded  most  interesting  information  respecting  the 
physical  constitution  of  the  sun. 

Now  we  notice  at  once  how  importantly  these 
researches  into  the  sun's  structure  bear  upon  the  sub- 
ject of  this  treatise.  It  would  be  indeed  interesting 
to  consider  the  actual  condition  of  the  central  orb  of 
the  planetary  scheme,  to  picture  in  imagination  the 
metallic  oceans  which  exist  upon  his  surface,  the  con- 
tinual evaporation  from  those  oceans,  the  formation  of 
metallic  clouds,  and  the  downpour  of  metallic  showers 

the  nature  of  these  vapors  and  of  the  discharge  itself,  the  relative  inten- 
sity of  the  component  parts  of  the  spectrum  will  be  variable. 

Lastly,  the  appearance  of  the  spectrum  belonging  to  any  element 
will  vary  according  to  the  circumstances  of  pressure  and  temperature 
under  which  the  element  may  emit  light. 


;8  OTHER    WORLDS  THAN  OURS. 

upon  the  surface  of  the  sun.  But  apart  from  such 
considerations,  and  viewing  KirchhofFs  discoveries 
simply  in  their  relation  to  the  subject  of  other  worlds, 
we  have  enough  to  occupy  our  attention. 

If  it  could  have  been  shown  that,  in  all  probabil- 
ity, the  substance  of  the  sun  consists  of  materials 
wholly  diiferent  from  those  which  exist  in  this  earth, 
the  conclusion  obviously  to  be  drawn  from  such  a 
discovery  would  be  that  the  other  planets  also  are 
differently  constituted,  "We  could  not  find  any  just 
reason  for  believing  that  in  Jupiter  or  Mars  there  ex- 
ist the  elements  with  which  we  are  acquainted,  when 
we  found  that  even  the  central  orb  of  the  planetary 
system  exhibits  no  such  feature  of  resemblance  to  the 
earth.  But  now  that  we  know,  quite  certainly,  that 
the  familiar  elements  iron,  sodium,  and  calcium,  exist 
in  the  sun's  substance,  while  we  are  led  to  believe  with 
almost  perfect  assurance  that  all  the  elements  we  are 
acquainted  with  also  exist  there,  we  see  at  once  that, 
in  all  probability,  the  other  planets  are  constituted 
in  the  same  way.  There  may  of  course  be  special 
differences:  in  one  planet  the  proportionate  distribu- 
tion of  the  elements  may  differ,  and  even  differ-  very 
markedly,  from  that  which  prevails  in  some  other 
planet.  But  the  general  conclusion  remains  that  the 
planets  are  formed  of  the  elements  which  have  so  long 
been  known  as  terrestrial ;  for  we  cannot  recognize 
any  reason  for  believing  that  our  earth  alone,  of  all 
the  orbs  which  circle  around  the  sun,  resembles  that 
great  central  orb  in  general  constitution.* 

*  It  will  be  seen,  in  the  chapter  on  Meteors  and  Comets,  that  this 


WHAT  WE  LEARN  FROM  THE  SUN. 


,  we  have  in  this  general  law  a  means  of  passing 
beyond  the.bounds  of  the  solar  system,  and  forming  no 
indistinct  conceptions  as  to  the  existence  and  character 
of  worlds  circling  around  other  suns.  For  it  will  be 
seen,  in  the  chapter  on  the  stars,  that  these  orbs,  like 
our  sun,  contain  in  their  substance  many  of  the  so- 
called  terrestrial  elements,  while  it  may  not  unsafely 
be  asserted  that  all,  or  nearly  all,  those  elements,  and 
few  or  no  elements  unknown  to  us,  exist  in  the  sub- 
stance of  every  single  star  that  shines  upon  us  from  the 
celestial  concave.  Hence  we  conclude  that  around 
those  suns  also  there  circle  orbs  constituted  like  them- 
selves, and  therefore  containing  the  elements  with 
which  we  are  familiar.  And  the  mind  is  immediately 
led  to  speculate  on  the  uses  which  those  elements  are 
intended  to  subserve.  If  iron,  for  example,  is  present 
in  some  noble  orb  circling  around  Sirius,  we  speculate 
not  unreasonably  respecting  the  existence  on  that  orb 
—  either  now  or  in  the  past,  or  at  some  future  time  — 
of  beings  capable  of  applying  that  metal  to  the  useful 
purposes  which  man  makes  it  subserve.  The  imagi- 
nation suggests  immediately  the  existence  of  arts  and 
sciences,  trades  and  manufactures,  on  that  distant 
world.  We  know  how  intimately  the  use  of  iron  has 
been  associated  with  the  progress  of  human  civiliza- 
tion, and  though  we  must  ever  remain  in  ignorance 
of  the  actual  condition  of  intelligent  beings  in  other 
worlds,  we  are  yet  led,  by  the  mere  presence  of  an 
element  which  is  so  closely  related  to  the  wants  of 

conclusion  has  a  most  important  bearing  on  the  views  we  are  to  form 
respecting  the  original  formation  of  the  planetary  scheme. 


So  OTHER   WORLDS  THAN  OURS. 

man,  to  believe,  with  a  new  confidence,  that  for  such 
beings  those  worlds  must  in  truth  have .  been  fash- 
ioned. 

I  would  fain  dwell  longer  on  the  thoughts  sug- 
gested by  the  researches  of  Kirchhoff.  Gladly  too 
would  I  enter  at  length  on  an  account  of  those  inter- 
esting discoveries  which  have  been  made  in  connection 
with  the  last  two  total  eclipses  of  the  sun.  The  re- 
quirements of  space,  however,  and  some  doubt  as  to 
the  direct  bearing  of  the  last-named  discoveries  on  the 
subject  I  have  in  hand,  warn  me  to  forbear.  One 
point,  however,  remains,  which  is  too  intimately  con- 
nected with  my  subject  to  be  passed  over. 

I  refer  to  the  sun's  corona. 

It  has  been  proved  that  the  solar  prominences  con- 
sist of  glowing  vapors,  hydrogen  being  their  chief 
constituent.  It  has  been  found  also,  by  comparing 
Mr.  Lockyer's  observations  of  the  prominence-spectra 
with  Dr.  Frankland's  elaborate  researches  into  the 
peculiarities  presented  by  the  spectrum  of  hydrogen 
at  different  pressures,  that  even  in  the  very  neigh- 
borhood of  the  solar  photosphere,  these  vapors  prob- 
ably exist  at  a  pressure  so  moderate  as  to  indicate 
that  the  limits  of  the  sun's  vaporous  envelope  can- 
not lie  very  far  (relatively)  from  the  outer  solar  cloud- 
layer. 

Now,  the  solar  corona  has  been  seen,  during  total 
eclipses  of  the  sun,  to  extend  to  a  distance  at  least 
equal  to  the  sun's  diameter  from  the  eclipsed  orb.  So 
that,  assuming  the  corona  to  be  a  solar  atmosphere,  it 
would  have  a  depth  of  about  eight  hundred  and  tiffry 


WHAT  WE  LEARN  FROM  THE  SUN.  61 

thousand  miles,  and  being  also  drawn  toward  the  sun 
by  his  enormous  attractive  energy  (exceeding  more 
than  twenty-seven  times  that  of  the  earth),  it  could 
not  fail  to  exert  a  pressure  on  his  surface  exceeding 
many  thousand  fold  that  of  our  air  upon  the  earth. 
In  fact,  such  an  atmosphere,  let  its  outermost  layers 
be  as  rare  as  we  can  conceive,  would  yet  have  its 
lower  layers  absolutely  liquefied,  if  not  solidified,  by 
the  enormous  pressure  to  which  they  would  be  sub- 
jected. We  cannot,  then,  believe  this  corona  to  be  a 
solar  atmosphere. 

Yet  it  is  quite  impossible  to  dissociate  the  corona, 
either  wholly  or  in  part,  from  the  sun.  I  am  aware 
that  physicists  of  eminence  have  attempted  to  do  this, 
and  not  only  so,  but  to  make  of  the  zodiacal  light  a 
terrestrial  phenomenon.  But  they  have  overlooked 
considerations  which  oppose  themselves  irresistibly  to 
such  a  conclusion. 

In  the  first  place,  the  mere  fact  that,  during  a 
total  eclipse,  the  moon  looks  black,  in  the  very  heart 
of  the  corona,  affords,  when  properly  understood,  the 
most  conclusive  evidence  that  the  light  of  the  corona 
comes  from  behind  the  moon.  If  the  glare  of  our 
atmosphere  could  by  any  possibility  account  for  the 
corona  (which  is  not  the  case),  then  that  glare  should 
appear  over  the  moon's  disk  also.  That  this  is  so  is 
proved  by  the  fact  that,  when  the  glare  really  does 
cover  the  moon,  as  while  the  sun  is  but  slightly 
eclipsed,  the  moon  is  not  projected  as  a  black  disk  on 
the  background  of  the  sky,  though,  where  her  outline 
crosses  the  sun,  it  appears  black,  by  contrast  with  the 


52  OTHER   WORLDS  THAN  OURS. 

intensity  of  his  light.*     The  point  seems,  however, 
too  obvious  to  need  discussion. 

And,  secondly,  as  Mr.  Baxendell  has  pointed  out, 
during  totality  the  part  of  the  earth's  atmosphere 
between  the  eye  and  the  corona  is  not  illuminated  by 
the  sun.  Over  a  wide  space  all  round  the  sun  we  are 
looking  through  an  atmosphere  which  is  completely 
dark.  Infact,  if  the  earth's  atmosphere  alone  were 
in  question,  we  ought  to  see  a  dark  or  negative  co- 
rona around  the  sun,  the  illuminated  atmosphere  only 
beginning  to  be  faintly  visible  at  a  considerable  angu- 
lar distance  from  the  sun.  This  argument,  rightly 
understood,  is  altogether  decisive  of  the  question.f 

*  It  is  also  shown  most  conclusively,  by  a  photograph  of  the  eclipse 
of  August,  1868,  taken  an  instant  before  the  totality.  Here  we  see  the 
glare  trenching  upon  the  moon's  disk  (elsewhere  black),  as  it  should 
theoretically.  So  soon  as  totality  commenced,  the  glare  had  reached  the 
moon's  limb,  whence  it  must  immediately  have  passed  quickly  away. 

f  In  fact,  if  we  take  the  mode  of  reasoning  by  which  Mr.  Lockyer 
has  endeavored  to  get  over  certain  physical  difficulties  presently  to  be 
mentioned,  we  shall  be  able  to  point  definitely  to  the  place  where  his 
argument  fails.  He  says,  conceive  a  tiny  moon  placed  so  as  to  appear 
coincident  with  the  centre  of  the  sun's  disk.  There  will  be  atmospheric 
glare  as  well  as  direct  sunlight.  Now,  conceive  this  small  moon  to 
expand  until  it  all  but  covers  the  sun.  Still  there  will  be  glare  and  a 
certain  small  proportion  of  direct  sunlight.  So  far  his  reasoning  is 
most  just.  But  when  he  allows  his  expanding  moon  to  cover  the  sun, 
and  to  extend  beyond  the  solar  disk  as  in  total  eclipse,  the  atmospheric 
glare  can  no  longer  be  assumed  to  exist  all  round  the  expanding  moon  : 
at  the  moment  when  the  moon  just  hides  the  sun,  the  glare  begins  to 
leave  the  moon,  a  gradually-expanding  black  ring  being  formed  round 
that  body.  It  is  only  necessary  to  consider  where  the  glare  comes  from 
to  see  that  this  must  be  so. 

I  have  taken  no  account  of  diffraction  here,  because  it  has  been 
abundantly  proved  that  no  corona  of  appreciable  width  could  be  formed 
around  the  moon  during  total  eclipse  by  the  diffraction  of  the  rays  of 
light  as  they  pass  near  the  moon's  limb. 


WHAT  WE  LEARN  FROM  THE  SUN.  63 

But  the  spectroscope  lias  given  certain  very  per- 
plexing evidence  respecting  the  light  of  the  corona, 
and  it  remains  that  we  should  endeavor  to  see  how 
that  evidence  bears  on  the  interesting  problem  which 
the  corona  presents  to  our  consideration. 

During  the  total  eclipse  of  last  August  the  Ameri- 
can observers  found  that  the  spectrum  of  the  corona 
is  continuous,  but  crossed  by  certain  bright  lines.  If 
we  accept  the  absence  of  dark  lines  as  established  by 
the  evidence  (which  is  doubtful),  this  result  seems  at 
first  sight  very  difficult  to  explain.  Referring  to  the 
principles  of  spectroscopic  analysis  stated  at  pp.  56,  57, 
it  will  be  seen  that  we  should  be  led  to  infer  that  the 
corona  consists  of  incandescent  matter  surrounded  by 
certain  glowing  gases.  It  is  difficult  to  suppose  that 
this  is  the  real  explanation  of  the  phenomenon. 

Mr.  Lockyer  suggests  that,  if  the  corona  shone  by 
reflecting  the  solar  light,  the  continuous  spectrum 
might  be  accounted  for  by  supposing  the  light  from 
the  glowing  vapors  around  the  sun  to  supply  the 
part  wanting  where  the  solar  dark  lines  are,  and  that 
some  of  these  vapors  shining  yet  more  brightly  would 
exhibit  their  bright  lines  upon  the  continuous  back- 
ground of  the  spectrum.  This  view,  as  applied  by 
Mr.  Lockyer  to  the  theory  that  the  corona  is  a 
terrestrial  phenomenon,  is  untenable,  for  the  reasons 
already  adduced.  But,  independently  of  those  reasons, 
there  are  others  which  render  such  a  solution  of  the 
difficulty  unavailable. 

Now,  remembering  that  we  have  two  established 
facts  for  our  guidance, — (i.)  the  fact  that  the  corona 


54  OTHER    WORLDS  THAN  OURS. 

cannot  be  a  solar  atmosphere,  and  (ii.)  the  fact  that  it 
must  be  a  solar  appendage — I  think  a  way  may  be 
found  toward  a  satisfactory  explanation. 

Let  it  be  premised  that  the  bright  lines  of  the 
coronal  spectrum  correspond  in  position  to  those  seen 
in  the  spectrum  of  the  aurora,  and  that  the  same  lines 
are  seen  in  the  spectrum  of  the  zodiacal  light,  and  in 
that  of  the  phosphorescent  light  occasionally  seen  over 
the  heavens  at  night. 

Since  we  have  every  reason  to  believe  that  the  light 
of  the  aurora  is  due  to  electrical  discharges  taking 
place  in  the  upper  regions  of  the  air,  we  are  invited  to 
the  belief  that  the  coronal  light  may  be  due  to  similar 
discharges  taking  place  between  the  particles  (of  what- 
ever nature)  constituting  the  corona. 

!Nfow,  though  the  appearance  of  an  aurora  is  due 
to  some  special  terrestrial  action  (however  excited),  yet 
the  material  substances  between  which  the  discharges 
take  place  must  be  assumed  to  be  at  all  times  present 
in  the  upper  regions  of  air.  In  all  probability,  they 
are  the  particles  of  those  meteors  which  the  earth 
is  continually  encountering.  And  since  we  know  that 
meteor-systems  must  be  aggregated  in  far  greater 
numbers  near  the  sun  than  near  the  earth,  we  may 
regard  the  coronal  light  as  due  to  electrical  dis- 
charges excited  by  the  sun's  action,  and  taking  place 
between  the  members  of  such  systems.  Besides  this 
light,  however,  there  must  necessarily  be  a  large  pro- 
portion of  light  reflected  from  these  meteoric  bodies. 
In  this  way  the  peculiar  character  of  the  coronal 
spectrum  may  be  readily  accounted  for.  We  know, 


WHAT  WE  LEARN  FROM  THE  SUN.  65 

from  the  auroral  spectrum,  that  the  principal  bright 
lines  due  to  the  electrical  discharges  would  be  precisely 
where  we  see  bright  lines  in  the  coronal  spectrum. 
But,  besides  these,  there  would  be  fainter  bright  lines 
corresponding  to  the  various  elements  which  exist  in 
the  meteoric  masses.  These  elements,  we  know,  are 
the  same  as  those  in  the  substance  of  the  sun.  Thus 
the  bright  lines  would  correspond  in  position  with  the 
dark  lines  of  the  solar  spectrum.  Hence,  as  light  re- 
flected by  the  meteors  would  give  the  ordinary  solar 
spectrum,  there  would  result  from  the  combination  a 
continuous  spectrum,  on  which  the  bright  lines  first 
mentioned  would  be  seen,  as  during  the  American 
eclipse. 

"What  the  polariscope  has  told  us  respecting  the 
corona  is  in  accordance  with  this  view. 

In  the  same  way  the  quality  of  the  zodiacal  light 
admits  of  being  perfectly  accounted  for,  without  re- 
sorting to  the  hypothesis  that  this  phenomenon  is  a 
terrestrial  one.* 

The  explanation  thus  put  forward  has  at  least  the 
advantage  of  being  founded  on  well-established  rela- 
tions. We  know  that  the  auroral  light  is  associated 
with  the  earth's  magnetism,  and  that  meteoric  bodies 

*  It  was  with  some  surprise  that,  at  a  late  meeting  of  the  Royal 
Astronomical  Society,  I  heard  Dr.  Balfour  Stewart  put  forward,  even 
as  a  hypothesis,  so  startling  a  proposition  as  this.  That  the  region  of 
the  counter-trades  may  be  at  times  illuminated  by  electrical  discharges 
will  serve  to  account  very  well  for  the  occasional  phosphorescent  appear- 
ance of  the  whole  heavens  at  night — but  the  portion  of  the  heavens 
illuminated  by  the  zodiacal  light  has  no  relation  whatever  to  the  atmos- 
pheric region  in  which  the  counter-trades  prevail.  The  hypothesis, 
indeed,  is  wholly  untenable. 


66  OTHER    WORLDS  THAN  OURS. 

are  continually  falling  upon  the  earth's  atmosphere. 
We  know,  also,  that  the  sun  exerts  magnetic  influences 
a  thousand-fold  more  intense  than  those  of  the  earth, 
and  that  in  his  neighborhood  there  must  be  many 
million  times  more  meteoric  systems. 

Bat  we  have  other  and  independent  reasons,  which 
must  not  be  overlooked,  for  considering  the  corona  to 
be  of  some  such  nature  as  I  have  suggested.  Lever- 
rier  has  shown  that  there  probably  exists  in  the  neigh- 
borhood of  the  sun  a  family  of  bodies  whose  united 
mass  suffices  appreciably  to  affect  the  motions  of  the 
planet  Mercury.  It  would  not  be  safe  to  neglect  con- 
siderations thus  vouched  for. 

Mr.  Baxendell,  also,  has  shown  that  certain  periodic 
variations  in  the  earth's  magnetism  point  to  the  ex- 
istence of  such  a  family  of  bodies ;  and  he  has  been 
able  to  assign  to  them  a  position  according  well  with 
that  determined  by  Leverrier. 

Now,  whatever  opinion  we  form  as  to  the  exact 
character  of  the  system  of  bodies  pointed  to  by  the 
researches  of  Leverrier  and  Baxendell — whether  we 
suppose  that  system  to  form  a  zone  around  the  sun,* 
or  that  (as  I  believe)  the  system  is  merely  due  to  the 
aggregation  of  meteoric  perihelia  in  the  sun's  neigh- 
borhood— we  may  be  quite  certain  of  this,  that  during 
a  total  solar  eclipse  the  system  could  not  fail  to  become 

*  I  am  not  here  referring  to  Hutnboldt's  notion  that  the  zodiacal 
light  is  due  to  a  zone  of  small  bodies  round  the  sun ;  a  view  which  only 
derives  importance  from  the  fact  that  Sir  John  Herschel  has  been  at  the 
pains  to  contradict  it.  It  need  hardly  be  said,  that  Sir  John  Herschel'a 
opinion  has  a  weight  which  is  altogether  wanting  to  Humboldt's,  so  fai 
as  astronomical  matters  are  concerned. 


WHAT  WE  LEARN  FROM  THE  SUN.  67 

risible.  Hence  there  is  a  double  objection  to  the  view 
put  forward  by  Mr.  Lockyer  and  others.  In  the  first 
place,  it  fails  to  account  for  the  appearance  presented 
by  the  corona ;  in  the  second  place,  it  fails  to  render  an 
account  of  the  implied  non-appearance  of  the  system 
which,  according  to  the  researches  of  Leverrier  and 
Baxendell,  circles  around  the  sun. 

It  will  be  seen,  in  the  chapter  on  "  Meteors  and 
Comets,"  how  important  a  bearing  these  views  respect- 
ing the  nature  of  the  corona  have  upon  the  history  of 
the  solar  system.  It  has  been  partly  for  this  reason 
that  I  have  here  briefly  considered  the  matter;  but 
*;here  is  another  and  a  most  important  relation  in  which 
these  views  must  be  regarded. 

We  know  that  the  sun  is  the  sole  source  whence 
light  and  heat  are  plentifully  supplied  to  the  worlds 
which  circle  around  him.  The  question  immediately 
suggests  itself— Whence  does  the  sun  derive  those 
amazing  stores  of  force  from  whence  he  is  continually 
supplying  his  dependent  worlds  ?  We  know  that,  were 
the  sun  a  mass  of  burning  matter,  he  would  be  con- 
sumed in  a  few  thousand  years.  We  know  that,  were 
he  simply  a  heated  body,  radiating  light  and  heat  con- 
tinually into  space,  he  would  in  like  manner  have 
exhausted  all  his  energies  in  a  few  thousand  years — a 
mere  day  in  the  history  of  his  system.  Whence,  then, 
comes  the  enormous  supply  of  force  which  he  has 
afforded  for  millions  on  millions  of  years,  and  which 
also  our  reason  tells  us  he  will  continue  to  afford  while 
the  worlds  which  circle  around  him  have  need  of  it— 
in  other  words,  for  countless  ages  yet  to  come  ? 


58  OTHER   WORLDS  THAN  OURS. 

Now,  there  are  two  ways  in  which  the  solar  ener- 
gies might  be  maintained.  The  mere  contraction  of 
the  solar  substance,  Helmholtz  tells  us,  would  suffice  to 
supply  such  enormous  quantities  of  heat,  that  if  the 
heat  actually  given  out  by  the  sun  were  due  to  this 
cause  alone,  there  would  not,  in  many  thousands  of 
years,  be  any  perceptible  diminution  of  the  sun's 
diameter.  But,  secondly,  the  continual  downfall  of 
meteors  upon  the  sun  would  cause  an  emission  of 
heat  in  quantities  vast  enough  for  the  wants  of  all 
the  worlds  circling  round  him ;  while  his  increase  of 
mass  from  this  cause  would  not  be  rendered  perceptible 
in  thousands  of  years,  either  by  any  change  in  his  ap- 
parent size  or  by  changes  in  the  motions  of  his  family 
of  worlds.* 

It  seems  far  from  unlikely  that  both  these  process- 
es are  in  operation  at  the  same  time.  Certainly  the 
latter  is,  for  we  know,  from  the  motions  of  the  meteoric 
bodies  which  reach  the  earth,  that  myriads  of  these 
bodies  must  continually  fall  upon  the  sun.  And  if  the 
corona  and  zodiacal  light  really  be  due  to  the  existence 
of  nights  of  meteoric  systems  circling  around  the  sun, 
or  to  the  existence  in  his  neighborhood  of  the  peri- 
helia of  many  meteoric  systems,  then  there  must  be  a 


*  Altogether  undue  stress  has  been  laid  upon  the  probable  change  in 
the  length  of  the  year,  owing  to  the  downfall  of  meteors  upon  the  sun's 
mass.  It  is  forgotten  that  the  crowded  meteors  forming  the  solar  corona 
are  already  within  the  earth's  orbit,  and  therefore  already  produce  theii 
full  effect  on  the  length  of  the  year.  The  subsidence  of  all  these  bodies 
at  once  upon  the  sun  would  not  affect  the  length  of  the  year,  though  il 
would  lead  to  certain  modifications  in  the  secular  perturbations  of  the 
earth's  orbit  in  figure  and  position. 


WHAT  WE  LEARN  FROM  THE  BUN.  69 

supply  of  light  and  heat  from  this  source,  very  nearly 
if  not  quite  sufficient  to  account  for  the  whole  solar 
emission. 

It  is  well  worthy  of  notice,  too,  that  the  association 
between  meteors  and  comets  has  an  important  bear- 
ing on  this  question.  We  know  that  the  most  re- 
markable characteristic  of  comets  is  the  enormous  dif- 
fusion of  their  substance.  Now,  in  this  diffusion  there 
resides  an  enormous  fund  offeree.  The  contraction 
of  a  large  comet  to  dimensions  corresponding  to  a 
very  moderate  mean  density  would  be  accompanied 
by  the  emission  of  a  vast  supply  of  heat.  And  the 
question  is  worth  inquiring  into,  whether  we  can  in- 
deed assume  that  the  meteors  which  reach  our  atmos- 
phere are  solid  bodies,  and  not  rather  of  cometic  dif- 
fusion ;  since  it  is  difficult  otherwise  to  account  for 
the  light  and  heat  which  they  emit.  Friction  through 
the  rarer  upper  strata  of  our  atmosphere  will  certainly 
not  account  for  these  phenomena ;  nor,  I  think,  will 
the  compression  of  the  atmosphere  in  front  of  the  me- 
teors ;  on  the  other  hand,  the  sudden  contraction  of  a 
diffused  vapor  would  be  accompanied  by  precisely 
such  results.  But,  be  this  as  it  may,  it  is  certain  that 
a  large  portion  of  the  substance  of  every  comet  is  in  a 
singularly  diffused  state.  And  since  the  meteoric  sys- 
tems circling  in  countless  millions  round  the  sun  are, 
in  all  probability,  associated  in  the  most  intimate 
manner  with  comets,  we  may  recognize  in  this  diffu- 
sion, as  well  as  in  the  mere  downfall  of  meteors,  the 
source  of  an  enormous  supply  of  light  and  heat. 

And  lastly,  turning  from  our  sun  to  the  other  suns 


7o         OTHER  WORLDS  THAN  OURS. 

which  shine  in  uncounted  myriads  throughout  space, 
we  see  the  same  processes  at  work  upon  them  all. 
Each  star-sun  has  its  coronal  and  its  zodiacal  disks, 
formed  by  meteoric  and  cometic  systems ;  for  other- 
wise each  would  quickly  cease  to  be  a  sun.  Each  star- 
sun  emits,  no  doubt,  the  same  magnetic  influences 
which  give  to  the  zodiacal  light  and  to  the  solar  co- 
rona their  peculiar  characteristics.  And  thus  the 
worlds  which  circle  round  those  orbs  may  resemble 
our  own  in  all  those  relations  which  we  refer  to  ter- 
restrial magnetism,  as  well  as  in  the  circumstance 
that  on  them  also  there  must  be,  as  on  our  own  earth, 
a  continual  downfall  of  minute  meteors.  In  those 
worlds,  perchance,  the  magnetic  compass  directs  the 
traveller  over  desert  wastes  or  trackless  oceans ;  in 
their  skies,  the  aurora  displays  its  brilliant  streamers  ; 
while,  amid  the  constellations  which  deck  their  heav- 
ens, meteors  sweep  suddenly  into  view,  and  comets  ex- 
tend their  vast  length  athwart  the  celestial  vault,  a 
terror  to  millions,  but  a  subject  of  study  and  research 
to  the  thoughtful. 


CHAPTEK  HI. 

THE    INFEEIOE    PLACETS. 

IN  considering  the  habitability  of  various  portions 
of  the  solar  system,  we  have  to  draw  a  marked  distinc- 
tion between  the  planets  which  travel  within  the  orbit 
of  the  earth  and  those  which  lie  beyond  its  range. 
So  far,  indeed,  as  our  belief  in  these  orbs  being  in- 
habited is  concerned,  we  may  apply  the  same  process- 
es of  reasoning  to  one  set  of  planets  as  to  the  other. 
Until  it  has  been  demonstrated  that  no  form  of  life 
can  exist  upon  a  planet,  the  presumption  must  be  that 
the  planet  is  inhabited.  But  it  is  impossible  to  con- 
template the  various  members  of  our  solar  system, 
without  being  led  to  consider  their  physical  habitudes 
rather  with  relation  to  the  wants  of  such  creatures  as 
exist  upon  our  own  earth,  than  merely  with  reference 
to  the  existence  of  life  of  some  sort  upon  their  surface. 
Viewing  Yenus  and  Mercury  in  this  way,  we  have  a 
different  set  of  relations  to  deal  with  than  we  find 
among  the  outer  planets.  We  are  struck,  at  once,  with 
the  marked  effects  which  seem  associable  with  their 
comparative  proximity  to  the  sun's  orb.  This  feature 


7  2         OTHER  WORLDS  THAN  OURS. 

and  the  shortness  of  their  period  of  revolution — that 
is,  of  their  year — are  the  characteristic  peculiarities 
we  have  to  deal  with. 

I  would  willingly  pay  some  attention  here  to  the 
story  of  Yulcan,  the  planet  which  has  been  supposed 
to  circle  yet  more  closely  than  Mercury  around  the 
centre  of  our  system,  were  it  not  for  the  great  doubt 
in  which  the  existence  of  this  planet  seems  enshrouded. 
If,  on  the  one  hand,  we  have  the  evidence  of  Lescar- 
bault  that,  on  a  certain  day,  and  at  a  certain  hour,  he 
saw  a  dark  object,  round  like  a  planet,  crossing  the 
face  of  the  sun,  we  have  also  the  evidence  of  Liais, 
whose  name  is  much  better  known  among  astrono- 
mers, that  at  that  very  hour  there  was  no  such  object 
on  the  solar  disk.  There  is  nothing  to  render  the  ex- 
istence of  an  intra-Mercurial  planet  at  all  unlikely ; 
and  there  are  many  observations  which  scarcely  seem 
explicable  on  any  other  hypothesis.  Still,  as  yet  we 
have  not  that  clear  and  unmistakable  evidence  which 
would  permit  me  to  speak  of  Yulcan  as  a  planet 
known  to  astronomers,  and  I  wish,  while  within  the 
bounds  of  the  solar  system,  to  limit  myself  to  the  con- 
sideration of  bodies  which  have  been  recognized  and 
examined. 

Mercury  circles  around  the  sun  in  the  brief  period 
of  eighty-eight  days,  or  rather  less  than  three  of  our 
months.  So  that,  if  the  planet  has  seasons,  these  must 
be  severally  about  three  weeks  long.  His  distance 
from  the  sun  varies  between  somewhat  wide  limits, 
owing  to  the  eccentricity  of  his  orbit.  When  he  is 
nearest  to  the  sun,  he  receives  ten  and  a  half  times 


THE  INFERIOR  PLANETS.  73 

aiore  light  and  heat  from  that  luminary  thaii  we  do  ; 
but,  when  he  removes  to  his  greatest  distance,  the 
light  and  heat  he  receives  are  reduced  by  more  than 
one-half.  Even  then,  however,  the  sun  blazes  in  the 
skies  of  Mercury  with  a  disk  four  and  a  half  times  larger 
than  that  which  he  presents  to  the  observer  on  earth. 

Undoubtedly  these  peculiarities,  the  shortness  of 
the  Mercurial  year,  and  the  immense  amount  of  light 
and  heat  poured  by  the  sun  upon  the  planet,  are  cir- 
cumstances which  do  not  encourage,  at  first  sight,  the 
belief  that  any  creatures  can  subsist  upon  this  planet, 
resembling  those  with  which  we  are  familiar.  "We  see, 
at  once,  that  all  forms  of  vegetation  in  Mercury  must 
differ  in  a  very  striking  manner  from  those  which  exist 
upon  the  earth,  because  their  structure  has  to  be 
adapted  to  much  more  rapid  changes  of  temperature. 
And  the  existence  of  a  totally  distinct  flora  suggests 
at  once  the  belief  that  animal  life  on  Mercury  must  be 
very  different  from  what  we  see  around  us. 

Let  us,  however,  proceed  a  few  steps  farther. 

It  has  been  found  that  Mercury  rotates  upon  his 
axis,  and,  if  we  may  put  faith  in  the  observations  of 
Schroter,  the  Mercurial  day  is  only  a  few  minutes 
longer  than  our  own.  Eut,  though  the  fact  of  the 
planet's  rotation  has  been  observed,  it  has  not  been 
found  possible  to  determine  in  what  position  the  axis 
of  rotation  lies.  It  has  been  said  that  the  planet's 
equator  is  much  more  inclined  than  the  earth's  to  the 
plane  in  which  the  planet  travels ;  but  little  reliance 
can  be  placed  on  the  evidence  which  has  been  adduced 
in  favor  of  this  view. 
4 


74  OTHER   WORLDS  THAN  OURS. 

"We  are  thus  left  altogether  in  doubt  as  to  the  na- 
ture of  the  Mercurial  seasons.  That  the  planet  has 
seasons  of  some  sort  we  are  certain,  because,  even  if 
the  axis  were  so  placed  that  perpetual  spring  reigned 
upon  the  planet — I  mean,  that  the  days  and  nights 
were  at  all  times  and  in  all  places  equal — yet  his  vary- 
ing distance  from  the  sun  would  give  changes  of  tem- 
perature quite  as  marked  as  those  which  characterize 
our  seasons  in  England,  and  very  much  more  marked 
than  those  known  in  tropical  regions.  Of  course,  if 
this  is  the  actual  arrangement,  there  are  different  cli- 
mates in  different  parts  of  the  planet.  Near  his  poles, 
the  sun,  though  visible  for  half  the  Mercurial  day, 
attains  yet  but  a  low  elevation  above  the  horizon  ;  just 
as  he  does  on  a  spring  day  within  our  own  polar  cir- 
cles. At  the  equator  the  sun  passes  day  after  day  to 
the  zenith,  and  pours  down  upon  the  planet  an  amount 
of  light  and  heat  far  exceeding  the  light  and  heat  of 
our  tropical  climates.  A  sun  immediately  overhead, 
and  showing  a  diameter  varying  from  more  than  twice 
to  more  than  three  times  that  of  our  sun,  must  be  a 
noble  and  maybe  a  terrible  phenomenon  in  the  skies 
of  Mercury. 

There  is  yet  another  arrangement  by  which  to  a 
portion  of  the  planet,  at  any  rate,  the  Mercurial  sea- 
sons might  be  tempered.  If  his  axis  is  so  placed  that 
what  would  be  the  winter  season,  were  his  orbit  not 
eccentric,  takes  place,  for  one  hemisphere,  when  the 
planet  is  nearest  to  the  sun,  then  undoubtedly  it  may 
very  well  happen  (the  inclination  of  his  axis  being  suit- 
ably adjusted)  that  this  so-called  winter  season  is  the 


THE  INFERIOR  PLANETS. 


75 


warmest  part  of  the  year  for  that  hemisphere.  In  this 
case,  there  would  be  the  least  possible  violence  in  the 
succession  of  the  Mercurial  seasons  for  that  hemi- 
sphere. But  in  the  other  hemisphere  the  seasonal 
changes  would  be  correspondingly  intensified. 

In  either  of  these  cases,  it  is  readily  conceivable 
that  even  forms  of  life  resembling  those  we  are  ac- 
quainted with  on  earth  might  exist  on  Mercury,  and 
that  without  any  special  provision  for  tempering  the 
great  heat  and  light  of  the  sun.  Those  regions  which 
correspond  to  our  temperate  and  tropical  zones  would 
indeed  scarcely  be  habitable  ;  but  the  polar  regions  of 
the  planet  would  not  form  a  disagreeable  abode. 

If,  however,  the  equator  of  the  planet  is  very  much 
inclined  to  the  plane  in  which  Mercury  travels,  it  can- 
not be  doubted  that  no  form  of  life  known  upon  earth 
can  possibly  exist  upon  Mercury,  without  some  special 
arrangements  for  tempering  the  seasonal  changes. 
This  will  appear  when  we  come  to  deal  with  the  effect 
of  the  great  inclination  which  some  astronomers  have 
ascribed  to  the  equator  of  Venus,  and  therefore  we 
need  not  consider  the  relation  with  regard  to  Mercury, 
of  whose  axial  inclination  no  trustworthy  information 
has  hitherto  been  obtained. 

It  remains  for  us  to  consider  what  sort  of  provision 
may  have  been  made  to  temper  the  great  heat  poured 
by  the  sun  upon  Mercury. 

The  climate  of  a  planet,  considered  generally,  is 
largely  influenced  by  the  nature  of  the  planet's  atmos- 
phere. We  have  very  clear  evidence  on  this  point, 
in  the  effects  which  we  notice  on  our  own  earth.  If 


^6  OTHER   WORLDS  THAN  OURS 

we  ascend  to  the  summit  of  a  lofty  mountain,  we  find 
the  air  much  colder  than  at  its  base.  In  India,  though 
the  full  heat  of  a  tropical  sun  is  poured  day  after  day 
upon  the  snowy  summits  of  the  Himalayas,  yet  the 
air  continues  colder  than  in  the  bitterest  midwinter 
weather  experienced  by  us  in  England.  Not  that  the 
solar  rays  have  no  power.  The  heat  is,  in  reality,  even 
greater  than  on  the  plains,  because  it  has  not  been 
intercepted  by  vapor-laden  air.  But  the  air  itself  is 
not  heated.  Owing  to  its  extreme  rarity  and  dryness, 
it  neither  impedes  the  passage  of  the  sun's  heat  to  the 
earth,  nor  prevents  the  return  of  that  heat  from  the 
earth  by  radiation  or  reflection ;  and  this  very  fact, 
that  it  does  not  impede  the  passage  of  heat,  means 
nothing  else  than  that  the  air  does  not  become  heated.* 
We  have,  then,  so  far  as  a  rare  atmosphere  is  con- 
cerned, two  points  to  dwell  upon — the  readiness  with 
which  such  an  atmosphere  permits  the  sun's  heat  to 
reach  the  surface  of  a  planet,  and  the  readiness  with 
which  it  permits  the  planet's  heat  to  pass  away  into 
space.  Now,  we  might  feel  doubtful  which  of  these 


*  The  following  passage,  quoted  by  Prof.  Tyndall  from  Hooker's 
"  Himalayan  Journals,"  illustrates  the  peculiarities  referred  to  above : 
"  At  10,000  feet,  in  December,  at  9  A.  M.,  I  saw  the  mercury  mount  to 
132°,  while  the  temperature  of  shaded  snow  hardly  was  22°.  At  13,100 
feet,  in  January,  at  9  A.  M.,  it  has  stood  at  98°,  with  a  difference  of 
68.2°,  and  at  10  A.  M.  at  114°,  with  a  difference  of  81.4°,  while  the 
radiating  thermometer  on  the  snow  had  fallen  at  sunrise  to  0.7°."  Such 
observations  as  these  are  well  worth  studying.  It  is  interesting  to  con- 
sider that  at  the  summit  of  the  highest  peaks  of  the  Himalayas  the  mid- 
day  heat  of  the  sun  must  sometimes  be  near  if  not  above  the  boiling 
point  corresponding  to  those  places,  since  water  would  boil  on  Mouni 
Everest  at  a  temperature  of  little  more  than  160°. 


THE  INFERIOR  PLANETS.  77 

two  effects  was  chiefly  to  be  regarded,  were  it  not  that 
on  our  own  earth  we  have  experience  of  the  effects  of 
a  very  rare  atmosphere.  We  know  that  the  climate 
of  very  elevated  regions  is  relatively  much  cooler  than 
that  of  places  on  the  plain.  Thus  we  learn  that  the 
direct  heating  powers  of  the  sun  are  not  so  much  to 
be  considered,  in  judging  of  the  climate  of  any  region, 
as  the  quality  of  the  atmosphere. 

Yet  we  must  not  deceive  ourselves  by  inferring 
that  mere  rarity  of  atmosphere  can  compensate  fully 
for  an  increased  intensity  of  solar  heat.  It  is  not  truo 
that  the  climate  of  a  place  on  the  slopes  of  the  Andes 
or  the  Himalayas  corresponds  to  that  of  a  region  on 
the  plain  which  has  an  atmosphere  equally  warm. 
The  circumstances  are,  in  fact,  wholly  different.  On 
the  plain  there  is,  it  is  true,  the  same  amount  of  heat 
in  the  case  supposed :  but  the  air  is  denser  and  more 
moisture-laden ;  the  nights  are  warmer  because  the 
skies  are  less  clear  and  the  heat  escaping  from  the 
earth  is  intercepted  by  clouds  or  by  the  transparent 
aqueous  vapor  in  the  air ;  and,  lastly,  there  is  not  so 
great  a  contrast  between  the  warmth  of  the  air  and 
the  direct  heat  of  the  solar  rays. 

If  the  atmosphere  of  Mercury,  therefore,  be  exces- 
sively rare,  as  some  have  supposed,  so  as  to  afford  an 
Alpine  or  Himalayan  climate  in  comparison  with  the 
tremendous  heat  we  should  otherwise  ascribe  to  the 
climate  of  the  planet,  there  would  by  no  means  result 
a  state  of  things  resembling  that  with  which  we  are 
familiar  on  earth.  We  must  not,  in  our  anxiety  to 
people  Mercury  with  creatures  such  as  we  know  of. 


78  OTHER   WORLDS  THAN  OURS. 

blind  ourselves  to  the  difficulties  which  have  to  be 
encountered.  We  cannot  thin  the  Mercurial  air,  with- 
out adding  to  the  direct  effects  of  the  sun  upon  the 
Mercurial  inhabitants.  Whether  in  this  way  we  in- 
crease the  habitability  of  the  planet  may  be  doubted 
when  we  consider  that  the  direct  action  of  the  sun's 
rays  upon  the  tropical  regions  of  Mercury,  thus  de- 
prived of  atmospheric  protection,  would  produce  a 
heat  four  or  five  times  greater  than  that  of  boiling 
water.  It  will  hardly  be  thought  that  the  intense  cold 
in  the  shade,  or  during  the  Mercurial  night,  would  com- 
pensate for  so  terrible  a  heat.  In  fact,  this  view  of 
the  Mercurial  climate  would  lead  us  to  find  a  close 
resemblance  between  the  inhabitants  of  the  planet  and 
the  unfortunates  described  by  Dante  as  doomed 

•'  A  sofferir  torment!  e  caldi  e  gieli." 

It  would  seem  hard  to  believe  in  the  existence  of  any 
organized  forms  under  such  conditions,  unless  perhaps 
such  "  microscopic  creatures,  with  siliceous  coverings," 
as  Whewell  proposed  to  people  Yenus  with. 

However,  we  have  yet  to  consider  whether  an 
atmosphere  of  a  different  sort  might  not  be  better 
suited  to  the  requirements  of  Mercury.  We  have 
seen  the  effects  of  a  rare  atmosphere,  let  us  inquire 
into  those  which  might  be  ascribed  to  a  dense  one. 

The  ordinary  effect  of  a  dense  atmosphere  we  know 
to  be  an  increase  of  heat,  which  is  certainly  not  what 
we  require  in  the  case  of  Mercury.  Nor  are  we  fa- 
miliar with  any  region  upon  our  earth  in  which  a 
dense  atmosphere  produces  a  contrary  climatic  effect ; 


THE  INFERIOR  PLANETS.  79 

BO  that  we  have  no  analogy  to  support  us  in  the  belief 
that,  possibly,  a  dense  atmosphere  might,  under  par- 
ticular circumstances,  serve  to  guard  a  planet  from  the 
solar  rays.  It  seems  possible,  however,  that  an  atmos- 
phere might  be  so  constituted  as  to  remain  almost  con- 
stantly loaded  with  heavy  cloud-masses.  In  this  case, 
it  by  no  means  follows  that  such  effects  would  follow 
as  we  ordinarily  associate  with  a  moisture-laden  at- 
mosphere. Up  to  a  certain  point j  doubtless,  the  in- 
crease of  moisture  in  the  air  tends  to  an  increase 
of  warmth ;  because  the  aqueous  vapor  exercises  a 
greater  effect  in  preventing  the  escape  of  heat  from 
the  earth  than  in  guarding  the  earth  from  the  solar 
rays.  And,  as  I  have  said,  the  only  climatic  effect  we 
can  associate  with  the  frequent  presence  of  large 
quantities  of  aqueous  vapor  in  the  air,  or  therefore 
with  an  ordinarily  clouded  state  of  the  sky,  is  that  of 
a  general  increase  of  heat.  But,  just  as  we  know  that 
a  cloudy  day  is  not  necessarily  nor  even  commonly  a 
warm  day,  it  may  well  be  that  an  atmosphere  so  dense 
as  to  be  at  all  times  cloud-laden  serves  as  a  protection 
from  the  sun's  intense  heat.  So  that,  instead  of  assign- 
ing dense  atmospheres  exclusively  to  the  more  distant 
planets,  as  some  astronomers  have  done,  we  might  be 
led  to  see  in  an  envelope  of  great  density  the  means  of 
defending  the  inhabitants  of  Mercury  and  Yenus  from 
the  otherwise  unedurable  rays  of  their  near  neighbor 
the  sun. 

Although  Mercury  is  not  a  planet  which  can  be  satis- 
factorily examined  with  the  telescope,  yet,  so  far  as  can 
be  judged  from  his  aspect,  his  atmosphere  is  in  reality 


go  OTHER    WORLDS  THAN  OURS. 

much  denser  than  our  earth's,  and  loaded  with  cloud- 
masses  of  enormous  extent.  Still  the  evidence  on 
these  points  is  far  from  satisfactory ;  and  there  is  one 
peculiarity  of  the  planet  which  does  not  accord  with 
this  view  of  the  constitution  of  his  atmosphere.  Un- 
doubtedly, if  the  light  we  receive  from  Mercury  came 
from  a  cloudy  envelope,  it  would  be  more  brilliant  than 
the  light  we  should  receive  from  the  surface  of  con- 
tinents and  oceans.  In  fact,  the  most  brilliant  light 
we  could  receive  from  a  globe  of  a  given  size,  placed  at 
a  given  distance  from  the  sun,  would  be  that  which 
would  be  reflected  were  such  a  globe  covered  with 
clouds.  Now,  there  can  be  no  doubt  whatever  that 
Mercury  does  not  reflect  the  same  proportion  of  light 
from  his  surface  that  some  of  the  planets  do.  He 
would  be,  when  favorably  situated,  the  brightest  of  all 
the  planets,  were  this  so ;  *  though,  seen  as  he  always 
is,  on  the  bright  background  of  a  full  twilight  sky, 
he  would  not  make  so  striking  an  appearance  as 

*  Placing  Mercury  in  perihelion  and  at  his  elongation,  we  get  a  half 
disk,  the  planet  about  90,000,000  miles  from  us,  and  about  30,000,000 
from  the  sun,  his  diameter  about  3,000  miles.  Now,  if  we  wish  to  com- 
pare the  light  he  then  sends  us,  with  that  of  Jupiter  at  his  brightest,  on 
the  assumption  of  equal  reflective  powers,  we  must  take  Jupiter  at  'a 
distance  of  about  360,000,000  miles  from  us,  and  about  450,000,000 
miles  from  the  sun,  showing  a  full  disk,  his  diameter  about  90,000  miles 
(I  put  all  the  numbers  mtnd,  for  convenience  of  calculation).  We  find, 
then,  that  the  ratio  of  Mercury's  light  to  Jupiter's  is 

1 (3,000)8 t (90,000)" 

2  (90,000,000)'2  x  (30,000,000)2  '  (360,000,000)2  x  (450,000,000)2 
or  •}  (4)2  (15)8  :  (30)2,  or  exactly  2  to  1. 

The  observation  above  cited  is  sufficient  to  prove  that  a  very  different 
state  of  things  actually  prevails ;  in  other  words,  that  the  reflective 
powers  of  the  two  planets  are  very  different.  Unless,  indeed,  Jupite» 
shines  in  part  by  inherent  light. 


THE  INFERIOR  PLANETS.  81 

Jupiter  does  when  in  opposition.  This,  however,  is 
not  the  case.  I  remember  being  much  struck  by  the 
superior  light  of  Jupiter,  on  the  afternoon  of  February 
23,  1868,  when  the  two  planets  were  very  close  to- 
gether, Mercury  being  nearly  at  his  brightest,  whereas 
Jupiter,  then  near  conjunction,  was  considerably  less 
bright  than  when  in  opposition.  Yenus  was  close  by, 
and  outshone  both  Mercury  and  Jupiter. 

It  seems  difficult,  therefore,  to  believe  that  the 
light  of  Mercury  comes  from  a  cloudy  envelope.  But 
there  is  still  one  supposition  which  may  restore  our  be- 
lief in  the  habitability  of  the  planet  by  creatures  not 
very  different  from  those  which  inhabit  our  earth.  If 
it  has  a  double  cloud-envelope,  the  upper  like  our  cir- 
rus clouds,  less  compact  than  the  lower,  and  permit- 
ting a  portion  of  the  sunlight  to  pass  through,  it  is 
possible  that  the  lower  cloud-layer  would  be  seen 
partly  in  shadow.  I  must  admit  that  the  explanation 
is  not  quite  satisfactory,  because,  just  as  much  light  as 
the  outer  clouds  intercepted  they  would  reflect ;  still, 
it  is  conceivable  that  the  usual  arrangement  of  these 
clouds  may  be  such,  that  to  us,  who  do  not  look  at  the 
planet  in  the  direction  in  which  the  sun's  rays  fall, 
but  somewhat  aslant,  the  shadows  of  the  upper  clouds 
upon  the  dense  and  compact  lower  envelope  may  be 
rendered  in  large  part  visible. 

After  all,  the  reader  may  prefer  the  view  which 
recognizes  in  the  polar  regions  of  Mercury  places 
suitable  for  organic  existences,  while  the  equatorial 
and  neighboring  regions  are  zones  of  fire,  whose  dan- 
gers the  bravest  Mercurials,  the  very  Livingstones 


32  OTHER   WORLDS  THAX  OURS. 

upon  that  planet,  would  not  dare  to  face.  AYe  may 
picture  to  ourselves,  on  this  view,  the  various  con- 
trivances by  which  the  inhabitants  of  the  two  polar 
(that  is,  in  reality,  temperate)  circles  manage  to  com- 
municate. There  may  be  regions  where  favoring  cir- 
cnmstances  narrow  the  uninhabitable  zone  so  much 
that  the  inhabitants  of  one  polar  circle  may  travel  to 
the  other  (or,  at  least,  cross  the  most  dangerous  por- 
tion of  the  hot  zone)  in  the  course  of  the  Mercurial 
night  Or  perhaps  tunnels  may  be  run,  or  sheltered 
cuttings  made,  along  which  the  voyage  may  be  made 
in  comparative  safety.  Ocean  communication  there 
can  be  none,  if  the  Mercurial  skies  are  clear,  since  the 
sun's  heat  on  the  tropical  zone  would  suffice  to  boil 
away  any  water  which  might  find  its  way  there. 

Certainly,  the  smallness  of  the  planet  and  the  di- 
minished effects  of  gravity  upon  its  surface  would 
tend  to  make  communication  much  easier,  and  the 
construction  of  protective  tunnels  or  cuttings  a  com- 
paratively light  task.  What  the  exact  force  of  grav- 
ity at  the  surface  of  Mercury  may  be  we  do  not  know, 
because  our  means  of  determining  the  mass  of  the 
planet  are  not  so  satisfactory  as  in  the  case  of  the 
other  primary  members  of  the  solar  system.  If  Mer- 
cury had  a  satellite,  we  could  tell  his  weight  at  once. 
If  he  were  as  large  as  Venus,  we  could  tell  his  weight 
by  observing  his  effect  in  disturbing  the  motions  of 
that  planet.  Aa  it  is,  the  only  means  we  have  of 
weighing  Mercury  is  the  observation  of  his  effect  in 
,listurbing  any  comet  which  may  pass  near  him.  In 
this  way  the  planet  has  been  weighed,  but  the  balance 


THE  INFERIOR  PLANETS.  83 

thus  employed  is  not  a  satisfactory  one  altogether,  be- 
cause we  are  not  quite  certain  how  much  of  the  dis- 
turbance of  a  comet  when  near  Mercury  is  due  to  the 
planet's  attraction.  Formerly,  it  was  supposed  that 
the  mean  density  of  Mercury  was  equal  to  that  of 
lead ;  but,  from  the  perturbations  of  Encke's  comet  in 
Mercury's  neighborhood,  astronomers  have  been  led  to 
the  conclusion  that  the  density  of  the  planet  is  not  more 
than  one-sixth  greater  than  our  earth's.  It  follows 
that,  as  his  diameter  is  little  more  than  three  thousand 
miles,  our  earth  is  about  fifteen  times  as  heavy  as 
Mercury.  Gravity  at  his  surface  is  such,  that  a  pound 
weight  of  ours  would  weigh  rather  less  than  seven 
ounces  on  Mercury.  Hence  the  creatures  which  seem 
to  us  most  unwieldy — the  elephant,  the  hippopotamus, 
and  the  rhinoceros,  or  even  those  vast  monsters,  the 
mammoth,  the  mastodon,  and  the  megatherium, 
which  bore  sway  over  our  globe  in  far-off  eras — might 
emulate  on  Mercury  the  agility  of  the  antelope  or  the 
greyhound. 

There  can  be  no  doubt  that,  where  gravity  acts  so 
feebly,  all  engineering  operations  would  be  rendered 
very  much  simpler — bridges  could  have  a  wider  span, 
and  yet  be  stronger  than  our  terrestrial  ones,  buildings 
could  be  loftier  and  yet  be  raised  more  easily,  and 
transit  of  all  sorts  would  be  effected  much  more  readily, 
while  at  the  same  time  the  distances  to  be  traversed  are 
very  much  less  than  on  our  earth,  since  the  surface  of 
Mercury  is  little  more  than  one-seventh  of  the  earth's. 

The  peculiarities  which  characterize  Venus  are  for 
the  most  part  similar  in  kind  to  those  we  have  had 


34  OTHER   WORLDS  THAN  OURS. 

to  consider  in  the  case  of  Mercury.  But  at  the  outset 
of  our  inquiries  into  the  physical  habitudes  of  this 
most  beautiful  planet,  we  must  point  to  the  striking 
resemblance  which  it  bears,  in  some  respects,  to  our 
own  earth.  So  far,  indeed,  as  telescopic  and  physical 
researches  have  yet  led  us,  the  planet  Mars,  as  we 
shall  presently  see,  appears  to  exhibit  habitudes  more 
closely  corresponding  to  those  we  are  apt  to  consider 
essential  to  the  wants  of  living  creatures.  But  in  size, 
in  situation,  and  in  density,  in  the  length  of  her  sea- 
sons and  of  her  rotation,  in  the  figure  of  her  orbit  and 
in  the  amount  of  light  and  heat  she  receives  from  the 
Bun,  Yenns  bears  a  more  striking  resemblance  to  the 
earth  than  any  orb  within  the  solar  system.  In  fact, 
there  is  no  other  pair  of  planets  between  which  so 
many  analogies  can  be  traced  as  between  Yenus  and 
the  earth.  Uranus  and  Neptune  are  similar  in  many 
respects,  but  they  differ  in  at  least  as  many.  Jupiter 
and  Saturn  are,  in  a  sense,  the  brother  giants  of  the 
solar  scheme,  while  the  dwarf  orbs  Mars  and  Mercury 
present  many  striking  points  of  similarity;  but  be- 
tween neither  of  these  pairs  can  we  trace  so  many  fea- 
tures of  resemblance  as  those  which  characterize  the 
twin  planets  Yenus  and  Terra,  while  the  features  of 
dissimilarity  in  either  pair  are  perhaps  even  more  ob- 
vious than  the  points  of  resemblance.  Had  Yenus 
but  a  moon  as  the  earth  has,  we  might  doubt  whether, 
in  the  whole  universe,  two  orbs  exist  which  are  so 
strikingly  similar  to  each  other. 

And  here  we  may  pause  for  a  moment  to  consider 
one  of  the  most  perplexing  enigmas  that  has  ever  been 


THE  INFERIOR  PLANETS.  85 

presented  to  astronomers.  Are  we  indeed  certain  that 
Venus  has  no  moon  ?  The  question  seems  a  strange 
one,  when  it  is  remembered  that  year  after  year 
Venus  has  been  examined  by  the  most  eminent  mod- 
ern observers,  armed  with  telescopes  of  the  most  ex- 
quisite defining  power,  without  any  trace  of  a  com- 
panion orb  being  noticed.  Nor,  indeed,  can  any 
reasonable  doubts  be  entertained  respecting  the  moon- 
less condition  of  Venus,  by  those  who  appreciate  the 
character  of  modern  telescopic  observations ;  and  yet, 
if  I  had  begun  this  paragraph  by  stating  the  evidence 
in  favor  of  the  existence  of  a  satellite,  I  believe  that 
nearly  every  reader  would  have  come  to  the  conclu- 
sion that  most  certainly  the  Planet  of  Love  has  an 
attendant  orb.  They  are  not  amateur  observers  only, 
who  have  seen  a  moon  attending  on  Venus,  but  such 
astronomers  as  Cassini  and  Short,  the  latter  with  two 
different  telescopes  and  four  different  eye-pieces. 
Four  times,  between  May  3  and  11,  1761,  Montaigne 
saw  a  body  near  Venus,  which  presented  a  phase 
similar  to  that  of  the  planet,  precisely  as  a  satellite 
would  have  done.  From  these  observations  M.  Bau- 
douin  deduced  for  the  new  star  a  diameter  of  about 
two  thousand  miles,  and  a  distance  from  Venus  nearly 
equal  to  that  which  separates  the  moon  from  the 
earth.  In  March,  1764,  again,  Rodkier  saw  the  enig- 
matical companion ;  Horrebow  saw  it  a  few  days 
later ;  and  Montbaron  saw  it  in  varying  positions  on 
March  15,  28,  and  29.  Lastly,  Scheuten,  who  wit- 
nessed the  transit  of  Venus  in  1761,  declares  that  he 
saw  a  satellite  accompany  Venus  across  the  face  of 


36  OTHER    WORLDS  THAN  OURS. 

the  sun.  So  that  we  cannot  be  greatly  surprised  that 
even  so  skilful  an  observer  as  the  late  Admiral  Smyth 
was  disposed  to  believe  in  the  existence  of  a  satellite 
of  Yenus.  "  The  contested  satellite  is,  perhaps,"  he 
remarked,  "  extremely  minute,  while  some  parts  of  its 
body  may  be  less  capable  of  reflecting  light  than 
others  ;  and  when  the  splendor  of  its  primary  and  our 
inconvenient  station  for  watching  it  are  considered,  it 
must  be  conceded  that,  however  slight  the  hope  may 
be,  the  search  ought  not  to  be  relinquished." 

There  is  little  occasion  to  dwell  upon  Yenus's 
moonless  condition,  because  the  inferior  planets  are 
much  less  affected  by  the  want  of  a  moon  than  a  supe- 
rior planet  would  be.  The  service  rendered  by  our 
own  moon,  as  a  luminary  of  the  night,  is  the  least 
important  work  she  does  in  our  behalf.  It  is  as  the 
chief  regulator  of  the  tides  that  the  moon  befriends 
us  most  usefully.  Now,  Yenus  has  no  need  of  lunar 
tides.  Assuming  that  she  has  oceans  such  as  those 
which  exist  upon  the  earth,  her  solar  tides  must  be 
about  two  and  a  half  times  as  high  as  the  solar  tides 
raised  in  our  own  oceans.  And  since  our  lunar  tidal 
wave  is  about  two  and  a  half  times  as  high  as  the 
solar  one,  we  have  tides  ranging  between  the  highest 
spring  tides,  which  are  three  and  a  half  times  as  high 
as  the  solar  tide  alone,  and  the  lowest  neap  tides, 
which  are  only  one  and  a  half  times  as  high  as  the 
solar  wave.  Yenus  has  constant  tides,  therefore,  cor- 
responding very  closely  to  the  mean  tides  on  our  own 
earth;  and  therefore  perfectly  well  adapted  to  sub- 
serve all  the  purposes  which  our  tides  render  us,  onlj 


THE  INFERIOR  PLANETS.  87 

with  less  variety  in  their  mode  of  operation.  Mer- 
cury also  has  sufficiently  high  solar  tides,  supposing  he 
has  extensive  oceans  (which  may  reasonably  be  ques- 
tioned), since  the  smallness  of  his  dimensions,  tending 
of  course  to  diminish  the  difference  of  action  on  which 
the  sun's  tidal  influence  depends,  is  fully  compensated 
by  his  great  proximity  to  that  orb. 

Venus  has  a  year  of  two  hundred  and  twenty-four 
days,  seventeen  hours,  very  nearly,  and  her  distance 
from  the  sun,  which  varies  little  during  the  course  of 
a  year,  is  somewhat  less  than  three-fourths  of  that 
which  separates  the  sun  from  us.  Her  day  is  about 
thirty-five  minutes  shorter  than  ours,  and  her  globe 
somewhat  smaller  than  the  earth's. 

It  is  clear  that,  merely  in  the  greater  proximity 
of  Yenus  to  the  sun,  there  is  little  to  render  at  least 
the  larger  proportion  of  her  surface  uninhabitable  by 
such  beings  as  exist  upon  our  earth.  The  sun,  as  seen 
in  her  skies,  has  a  diameter  one-third  larger  than  he 
presents  to  us ;  and  his  apparent  surface-dimensions, 
on  which,  of  course,  his  heating  and  illuminating 
powers  depend,  are  greater  in  the  proportion  of  about 
sixteen  to  nine.  This  undoubtedly  would  render  his 
heat  almost  unbearable  in  the  equatorial  regions  of 
Yenus,  but  in  her  temperate  and  sub-arctic  regions  a 
climate  which  we  should  find  well  suited  to  our  re- 
quirements might  very  well  exist ;  while  her  polar 
regions  might  correspond  to  our  temperate  zones,  and 
be  the  abode  of  the  most  active  and  enterprising  races 
existing  upon  her  surface. 

Here,  however,  we  have    been    supposing  that 


88  OTHER   WORLDS  THAN  OURS. 

Venus  has  seasons  resembling  our  own  in  character, 
— in  other  words,  that  her  axis  of  rotation  is  inclined 
at  about  the  same  angle  to  the  plane  in  which  she 
travels.  Observations  have  been  made,  according  to 
which  a  very  different  state  of  things  would  appear  to 
prevail.  It  has  been  said,  on  the  authority  of  ob- 
Bervers  of  some  eminence,  that  her  axis  is  inclined 
only  15°  to  the  plane  of  her  orbit.*  If  this  is  really 
the  case,  a  number  of  singular  and  somewhat  compli- 
cated relations  are  presented,  the  result  of  which  it 
may  be  interesting  to  exhibit  to  the  reader — espe- 
cially as  there  is  very  little  doubt  that  in  the  case  of 
Uranus  an  axial  peculiarity  of  this  sort  actually  exists,  f 

In  the  first  place,  the  arctic  regions  of  Yenus  ex- 
tend within  fifteen  degrees  of  her  equator  (if  the  axis 
is  really  bowed  as  supposed),  while  the  tropics  ex- 
tend within  fifteen  degrees  of  her  poles — so  that  two 
zones,  larger  by  far  than  the  temperate  zones  of 
our  earth,  belong  both  to  her  arctic  and  to  her 
tropical  regions.  It  is  difficult  to  say  whether  her 
equatorial,  her  polar,  or  her  arctico-tropical  regions 
would  be,  to  our  ideas,  the  least  pleasing  portion  of 
her  globe. 

An  inhabitant  of  the  regions  near  either  pole  has  to 

*  Why  is  it  that,  in  so  many  works  of  popular  astronomy,  the  mis- 
take is  made  of  giving  the  inclination  of  a  planet's  equator  to  the  orbit 
as  the  inclination  of  the  axis  to  that  plane  ?  In  nine  out  of  ten  astro- 
nomical works,  the  inclination  of  the  earth's  axis  to  her  orbit  is  given 
•s  23|° ;  were  this  the  case,  the  larger  part  of  the  earth  would  be  unin- 
habitable. 

•J-  If  the  observations  of  De  Vico  may  be  trusted,  the  inclination  of 
Venus,  though  less  than  75°,  is  still  so  considerable  (about  55°)  as  t« 
justify  the  general  conclusions  deduced  in  the  following  paragraphs. 


THE  INFERIOR  PLANETS.  89 

endure  extremes  of  heat  and  cold,  such  as  would  suffice 
to  destroy  nearly  every  race  of  living  beings  subsisting 
upon  the  earth.  During  the  summer,  the  sun  circles 
continually  close  to  the  point  overhead,  so  that,  day 
after  day,  he  pours  down  his  rays  with  an  intensity  of 
heat  and  of  light  exceeding  nearly  twofold  the  midday 
light  and  heat  of  our  own  tropical  sun.  Only  for  a 
short  time,  in  autumn  and  in  spring,  does  the  sun  rise 
and  set  in  these  regions.  A  spring  or  autumn  day, 
like  one  of  our  days  at  those  seasons,  lasts  about  twelve 
hours  ;  but  the  sun  attains  at  noon,  in  spring  or  autumn, 
a  height  of  only  a  few  degrees  above  the  horizon. 
Then  presently  comes  on  the  terrible  winter,  lasting 
about  three  of  our  months,  but  far  more  striking  in  its 
characteristics  even  than  the  long  winter  night  of  our 
polar  regions.  For,  near  our  poles,  the  sun  approaches 
the  horizon  at  the  hour  corresponding  to  noon ;  and 
though  he  does  not  show  his  face,  he  yet  lights  up  the 
southern  skies  with  a  cheering  twilight  glow.  But 
during  the  greater  part  of  the  long  night  of  Venus's 
polar  regions,  the  sun  does  not  approach  within  many 
degrees  of  the  horizon,  N"ay,  he  is  farther  below  the 
horizon  than  the  midnight  sun  of  our  arctic  regions. 
Thus,  unless  the  skies  are  lit  up  with  auroral  splen- 
dors, an  intense  darkness  prevails  during  the  polar 
winter,  which  must  add  largely  to  the  horrors  of  that 
terrible  season.  Certainly,  none  of  the  human  races 
upon  our  earth  could  bear  the  alternations  between 
these  more  than  polar  terrors  and  an  intensity  of 
summer  heat  far  exceeding  any  with  which  we  are 
familiar  on  earth. 


9° 


OTHER    WORLDS  THAN  OURS. 


Let  us  see  whether  the  equatorial  regions  are  more 
pleasing  abodes. 

In  these  parts  of  Yenus  there  are  two  summers, 
corresponding  to  the  spring  and  autumn  of  the  polar 
regions.  At  these  seasons,  the  sun  rises  day  after  day 
to  the  point  overhead,  and  the  weather  corresponds  for 
a  while  to  that  which  prevails  in  the  tropical  regions  of 
our  own  earth.  But  between  these  seasons  the  sun 
passes  away  alternately  to  the  northern  and  southern 
skies.  During  the  season  corresponding  to  summer, 
he  is  above  the  horizon  nearly  throughout  the  twenty- 
three  and  a  third  hours  of  Yenus's  day ;  *  but  he  at- 
tains no  great  elevation,  travelling  always  in  a  small 
circle  close  around  the  northern  pole.  During  the 
season  corresponding  to  winter,  he  is  above  the  horizon 
only  a  very  short  time  each  day,f  and  is  always  close 

*  On  the  equator  itself,  as  on  our  own,  the  day  is  always  equal  in 
length  to  the  night.  The  above  account  corresponds  to  a  place  near  the 
borders  of  the  equatorial  zone. 

f  In  Admiral  Smyth's  "  Celestial  Cycle,"  the  only  work  in  which,  so 
far  as  I  am  aware,  the  effects  of  the  inclination  ascribed  to  Yenus's  axis 
have  been  at  all  considered,  it  is  stated  that  in  the  year  of  Venus  there 
are  but  nine  and  a  quarter  of  her  days,  "  reckoned  by  the  sun's  rising 
and  setting,  owing  to  which  the  sun  must  appear  to  pass  through  a 
whole  sign  in  little  more  than  three-quarters  of  her  natural  day."  He 
does  not  give  any  reasons  for  this  remarkable  statement,  which  most 
certainly  is  not  correct.  In  all  places  outside  the  arctic  circles  of  Venus, 
the  year  contains  as  many  natural  days  as  there  have  been  rotations  of 
Venus,  wanting  one  only  (as  in  the  case  of  our  own  earth) ;  in  the  re- 
maining regions  there  will  be  more  or  fewer  days,  according  as  the 
station  considered  is  nearer  to  or  farther  from  the  arctic  circle.  Smyth's 
remark  that  the  varying  amplitude  of  the  sun  (his  distance,  that  is,  from 
the  east  and  west  points),  at  rising  or  setting,  would  give  travellers  on 
Venus  readier  means  than  our  seamen  have,  of  determining  the  longi- 
tude, is  just.  But  the  problems  involved  must  be  very  difficult,  and  T 


THE  INFERIOR  PLANETS.  9! 

to  the  south,  attaining  only  an  elevation  of  a  few  de- 
grees at  noon.  Thus  we  have  the  following  curious 
succession  of  seasons :  At  the  vernal  equinox  a  summer 
much  warmer  than  our  tropical  summers ;  about  fifty- 
six  days  later,  or  at  the  summer  solstice,  weather  resem- 
bling somewhat  the  spring  of  our  temperate  zones,  only 
that  the  night  is  exceedingly  short ;  yet  fifty-six  days 
later  there  is  another  summer,  as  terrible  as  the  for- 
mer ;  and  lastly,  at  the  winter  solstice,  the  days  are 
shorter  and  the  cold  probably  more  intense  than  in  the 
winter  of  places  near  our  arctic  circles.  In  such  regions 
the  contrasts,  rather  than  either  of  the  extremes  of 
climate,  would  be  most  trying  to  terrestrial  races ;  and 
it  is  scarcely  too  much  to  say  that  no  races  subsisting 
upon  our  earth  could  possibly  endure  such  remarkable 
changes,  succeeding  each  other  so  rapidly. 

Lastly,  the  beings  who  inhabit  the  wide  zones 
which  are  at  once  tropical  and  arctic  have  climates 
ranging  between  the  two  limits  just  considered.  If 
they  are  near  the  equatorial  regions,  they  suffer  from 
all  the  vicissitudes  of  the  equatorial  climate,  with  this 
further  tribulation,  that,  in  midwinter,  they  do  not  see 
the  sun  even  at  midday,  a  circumstance  by  no  means 
compensated  (according  to  our  ideas)  by  the  fact  that 
near  the  summer  solstice  the  sun  does  not  set.  If  they 
are  near  the  polar  regions,  they  have  a  summer  even 
more  terrible  than  the  polar  summer,  and  a  winter 
scarcely  less  dreary  and  bitter. 

wish  her  mathematicians  joy  of  them.  The  cadets  in  our  schools  and 
training-ships  have  an  easy  time  of  it,  compared  with  the  unfortunate 
beings  who  are  to  officer  the  ships  of  Yenus — always  supposing  her  axif 
is  inclined  as  we  have  been  assuming. 


92  OTHER   WORLDS   THAN  OURS. 

Fortunately  for  our  belief  in  the  habitabiiity  of 
Venus,  astronomers  are  far  from  accepting  with  con- 
fidence the  assertions  of  those  observers  who  have  as- 
signed to  Venus  an  inclination  so  remarkable.  If  her 
inclination  should  at  all  resemble  the  earth's,  there  is 
every  reason  to  believe  that  her  physical  habitudes 
also  resemble  those  of  the  earth.  In  this  case,  the 
argument  from  analogy,  presented  in  the  opening 
chapter  of  this  work,  seems  to  force  upon  us  the  con- 
clusion that  she  is  inhabited ;  while  we  may  believe, 
though  perhaps  with  less  confidence,  that  a  close  re- 
semblance subsists  between  the  creatures  which  people 
her  surface  and  those  with  which  we  are  acquainted. 

We  have  no  direct  evidence,  indeed,  on  which  to 
ground  our  belief  that  the  greater  proximity  of  Venus 
to  the  sun  may  not  be  accompanied  by  any  very  re- 
markable peculiarities  in  the  characteristics  of  her  cli- 
mate. But  we  have  an  indirect  argument  of  some 
strength.  If  Venus  is  much  nearer  than  the  earth  to 
the  sun,  the  earth,  in  turn,  is  much  nearer  to  the  sun 
than  Mars  is.  Yet,  as  we  shall  see  in  the  next  chap- 
ter, we  have  clear  evidence  from  telescopic  observa- 
tion, and  still  clearer  evidence  as  the  results  of  spec- 
troscopic  research,  that  the  climatic  arrangements  on 
Mars  do  not  differ  in  any  remarkable  degree  from 
those  of  our  own  earth.  It  would  follow,  therefore,  as 
at  least  probable,  that  a  similar  resemblance  prevails 
between  the  climate  of  the  earth  and  that  of  Venus. 
So  that,  despite  the  claim  which  Dr.  Whewell  has  put 
in  for  microscopic  animalcules  with  siliceous  coverings 
as  the  sole  inhabitants  of  Venus,  I  can  find  no  reason 


THE  INFERIOR  PLANETS. 


93 


(if  the  abnormal  axial  inclination  above  considered  is 
once  disproved)  for  denying  that  she  may  be  the  abode 
of  creatures  as  far  advanced  in  the  scale  of  creation  as 
any  which  exist  upon  the  earth. 

Gravity  at  the  surface  of  Venus  is  so  nearly  equal 
to  terrestrial  gravity,  that  the  difference  is  altogether 
insufficient  to  introduce  any  noteworthy  effects.  The 
delicate  adjustment  of  the  sap-passages  of  plants  to  the 
force  of  terrestrial  gravity,  which  Dr.  Whewell  notices 
in  his  '  Bridgewater  Treatise,'  might  indeed  be  dis- 
turbed, if  the  earth's  gravity  were  suddenly  made 
equal  to  that  of  Venus.  But  it  would  be  strangely  to 
limit  our  conception  of  Nature's  powers  of  adaptation, 
to  suppose  that  therefore  there  can  be  no  vegetation 
on  Venus  resembling  that  with  which  we  are  familiar. 

Venus  is  the  only  planet  the  extent  of  whose  at- 
mosphere has  been  carefully  estimated.  If  Venus  had 
no  atmosphere,  she  would  present,  when  horned,  a  semi- 
circular convexity  ;  whereas  the  refractive  effects  of  an 
atmosphere,  by  causing  the  sun  to  illumine  rather 
more  than  a  full  hemisphere,  would  tend  to  lengthen 
her  horns.  It  has  been  found  that  her  convexity  when 
she  is  horned  exceeds  a  semicircle,  and,  from  the  ob- 
served extent  of  this  excess,  it  has  been  calculated 
that  her  atmosphere  is  so  far  more  extensive  than  ours 
as  to  make  its  refractive  effects  on  a  body  near  the 
horizon  about  one-third  greater.  So  that,  as  this  is 
about  the  proportion  in  which  the  diameter  of  the  sun 
as  seen  from  Venus  exceeds  that  which  he  presents  to 
us,  the  inhabitant  of  Venus,  like  the  inhabitant  of  our 
earth,  sees  the  sun  fully  raised  above  the  horizon  at 


p4  OTHER    WORLDS  THAN  OURS. 

the  moment  when,  but  for  refraction,  his  orb  would  bo 
just  concealed  beneath  it. 

Of  the  constitution  of  the  atmosphere  of  Yenus  we 
know  little.  The  spectrum  of  her  light  shows  the  dark 
lines  which  belong  to  the  solar  spectrum,  and  the 
Padre  Secchi  has  noticed  certain  faint  lines,  which 
seem  to  indicate  the  presence  of  aqueous  vapor  in  the 
atmosphere  of  the  planet.  But  he  scarcely  gives  sat- 
isfactory evidence  that  the  lines  he  has  thus  seen  were 
not  due  to  the  absorption  exercised  by  aqueous  vapor 
in  our  own  atmosphere.  The  same  observer  finds,  in 
the  strengthening  of  the  nitrogen  lines  near  the  F  line 
of  the  spectrum,  evidence  that  the  atmosphere  of  Ye- 
nus is  constituted  very  similarly  to  the  air  we  breathe. 

On  the  whole,  the  evidence  we  have  points  very 
strongly  to  Yenus  as  the  abode  of  living  creatures  not 
unlike  the  inhabitants  of  earth.  With  the  sole  excep- 
tion of  the  inclination,  which  has  been,  without  suffi- 
cient evidence,  assigned  to  the  planet's  equator,  I  can 
see  nothing  which  can  reasonably  be  held  to  point  to 
an  opposite  conclusion.  Certainly  the  strong  light 
which  the  sun  pours  upon  Yenus  need  least  of  all  be 
objected  to,  since,  if  there  is  one  adaptative  power  which 
Nature  exhibits  more  clearly  than  another,  it  is  that 
by  which  the  various  creatures  we  are  acquainted  with 
are  enabled  to  live  in  comfort  under  all  degrees  of 
light,  from  the  obscurity  in  which  the  mole  pursues  his 
subterranean  researches,  to  the  blazing  light  of  the 
noonday  sun  toward  which  (in  fable,  if  not  in  fact)  the 
eagle  turns  his  unshrinking  eyes. 

There  is  one  peculiarity  which  yet  remains  to  be 


THE  INFERIOR  PLANETS.  95 

noticed.  Many  are  disposed  to  find,  in  the  beauty  of 
the  celestial  objects  which  deck  the  skies  of  different 
planets,  a  certain  proof  that  reasoning  beings  must 
exist  who  can  appreciate  the  display.  Surely  the 
argument  has  very  little  force,  since  we  know  that 
myriads  on  myriads  of  ages  must  have  passed,  during 
which  the  glories  of  our  own  heavens  were  displayed, 
night  after  night,  with  none  to  regard  them.  The 
moon  has  passed  through  all  her  phases,  the  star  of 
morning  and  of  eve  has  shed  its  soft  radiance  upon  the 
terrestrial  landscape,  Jupiter  and  Saturn  have  pursued 
their  stately  courses  among  the  fixed  stars,  and  the 
glories  of  those  constellations  which  shine  with  equal 
splendor  upon  all  the  planets  of  the  solar  scheme 
have  been  displayed  in  all  their  unchanging  magnifi- 
cence, while  as  yet  our  earth  was*  the  abode  but  oi 
hideous  reptiles,  or  of  yet  more  monstrous  creatures  in 
forest  and  in  plain. 

If  this  argument  were  really  of  force,  doubtless 
there  are  no  planets  in  the  whole  range  of  the  solar 
system  to  which  it  might  not  be  applied.  Each  has 
some  special  object  of  beauty  in  its  heavens,  which  is 
not  exhibited  to  the  rest.  Certainly  Mercury  and 
Venus  are  no  exceptions  to  this  rule.  The  inhabitant 
of  Mercury  sees  in  Yenus  an  orb  which,  when  favor- 
ably situated,  far  outshines  in  splendor  the  brightest 
of  the  planetary  orbs  seen  in  our  skies.  So  far,  indeed, 
as  light-giving  power  is  concerned,  Yenus  must  be  no 
contemptible  moon  to  the  Mercurials  when  she  is  nearly 
in  opposition.  Our  earth,  too,  with  its  companion 
moon,  must  form  a  noble  object  in  the  sky  of  Mercury, 


96  OTHER   WORLDS  THAN  OURS. 

though,  without  telescopic  aid,  the  moon  perhaps  may 
not  be  separately  visible.  To  the  inhabitants  of  Yenus, 
Mercury  and  the  earth  must  be  splendid  Objects.  The 
former  would  not  only  appear  much  larger  than  to 
ourselves,  but,  being  seen  almost  as  favorably  as  we 
Bee  Venus,  would  form  a  much  more  striking  object  in 
the  morning  or  evening  sky  of  that  planet.  The  earth, 
as  seen  by  the  inhabitants  of  Yenus,  must  shine  much 
more  splendidly  than  Jupiter  does  in  our  skies.  Our 
moon  must  be  distinctly  visible,  so  that,  without  the 
aid  of  any  telescope,  the  inhabitant  of  Yenus  has  such 
evidence  of  the  Copernican  theory  as  would  suffice,  if 
properly  handled,  to  rout  the  ranks  of  the  Ptolemaists, 
supposing  there  have  ever  been  people  in  Yenus  foolish 
enough  to  imagine  the  tiny  globe  they  live  upon  to  be 
the  centre  of  the  universe. 


CHAPTEE  IT.- 

MAES,   THE   IVONIATTJEE   OF   OUE   EAETH. 

IT  is  singular  that,  among  all  the  orbs  which  circle 
around  the  sun,  one  only,  and  that  almost  the  least  of 
the  primary  planets,  should  exhibit  clearly  and  unmis- 
takably the  signs  which  mark  a  planet  as  the  abode 
of  life.  We  have  examined  Mercury  and  Venus,  the 
only  other  orbs  which  belong,  like  the  earth  and  Mars, 
to  the  scheme  of  the  minor  planets,  and  we  have  found 
little  to  guide  us  to  any  certain  conclusion  respecting 
their  physical  habitudes.  When  we  pass  beyond  the 
wide  gap  which  separates  the  minor  planets  from  the 
giant  members  of  the  solar  family,  we  shall  find  much 
to  attract  our  admiration,  much  to  force  upon  us  the 
belief  that  these  orbs  have  been  created  to  be  the 
abodes  of  even  nobler  races  than  those  which  subsist 
upon  our  earth ;  but  we  shall  find  little  to  justify  us 
in  asserting  that  they  resemble  the  earth  in  those  habi- 
tudes which  seem  essential  to  the  wants  of  terrestrial 
races.  The  planet  Mars,  on  the  other  hand,  exhibits 
in  the  clearest  manner  the  traces  of  adaptation  to  the 
wants  of  living  beings  such  as  we  are  acquainted  with. 
Processes  are  at  work  out  yonder  in  space  which  ap- 

fi 


98  OTHER    WORLDS  THAN  OURS. 

pear  utterly  useless,  a  real  waste  of  Nature's  energies, 
unless,  like  their  correlatives  on  earth,  they  subserve 
the  wants  of  organized  beings. 

I  would  not  indeed  insist,  as  some  have  done,  too 
strongly  upon  this  argument.  I  know  that  on  every 
side  we  see  tokens  of  an  exuberant  activity  in  Nature, 
which,  according  to  our  ideas,  may  appear  to  savor  of 
wastefulness.  The  cloud  which  has  been  raised  by 
the  solar  energies  from  tropical  seas,  and  which  the 
winds  have  wafted  over  continents,  may  shed  its  waters 
on  the  sea  or  in  the  desert,  where  seemingly  they  are 
wholly  wasted.  Winds  may  spend  their  force  appar- 
ently in  vain.  And  in  a  thousand  ways  Nature's  busy 
forces  may  be  at  work  where  we,  in  our  short-sighted- 
ness, can  see  no  useful  purpose  which  they  subserve. 

But  there  is  a  marked  distinction  between  such 
apparent  instances  of  wasteful  action,  and  the  system- 
atic processes  which  are  taking  place  over  the  globe  of 
Mars. 

Little  as  we  can  appreciate  the  real  character  of 
Nature's  work  upon  our  earth,  we  can  yet  dimly  trace 
out  a  necessity  (depending  upon  the  order  which  actu- 
ally exists)  for  that  which  yet  appears  to  resemble 
waste.  "We  see,  for  instance,  that  if  a  country  or  a 
continent  is  to  be  provided  with  a  due  supply  of  rain, 
without  supernatural  intervention  at  every  step  of  the 
process,  that  result  can  only  be  secured  by  what  may 
be  described  as  a  random  distribution,  involving  always 
what  to  us  resembles  waste.  If,  out  of  a  thousand 
showers,  ten  only  fall  so  as  to  be  useful  to  the  land, 
the  object  of  Nature  is  subserved,  and  the  useful  rain- 


MARS,  THE  MINIATURE  OF  OUR  EARTH.         99 

falls  serve  to  explain  the  seemingly  wasted  ones.  In 
realitv,  of  course,  there  has  not  been  a  random  distri- 
bution, nor  has  there  been  any  waste  ;  I  infer,  merely, 
that  a  sort  of  purpose  is,  in  such  a  case,  dimly  seen, 
even  by  man,  who  can  see  so  short  a  distance  into  the 
workings  of  the  Almighty. 

But  in  the  case  of  Mars  we  have  no  such  explana- 
tion of  the  processes  we  observe,  if  we  dismiss  our  be- 
lief that  he  is  the  abode  of  living  creatures.  For  if 
Mars  be,  indeed,  untenanted  by  any  forms  of  life,  then 
these  processes  going  on  year  after  year,  and  century 
after  century,  represent  an  exertion  of  Nature's  ener- 
gies which  appears  absolutely  without  conceivable 
utility.  If  one  cloud,  out  of  a  hundred  of  those  which 
shed  their  waters  upon  Mars,  supplies  in  any  degree 
the  wants  of  living  creatures,  then  the  purport  of  those 
clouds  is  not  unintelligible  ;  but  if  not  a  single  race  of 
beings  peoples  that  distant  world,  then  indeed  we  seem 
compelled  to  say  that,  in  Mars  at  least,  Nature's  forces 
are  wholly  wasted.  Such  a  conclusion,  however,  the 
true  philosopher  would  not  care  needlessly  to  adopt. 

Let  us  consider  what  astronomy  has  taught  us  re- 
specting the  ruddy  planet. 

The  globe  of  Mars  is  about  five  thousand  miles  in 
diameter,  so  that  his  linear  dimensions  bear  to  those  of 
the  earth  the  proportion  of  about  five  to  eight.  His 
surface,  therefore,  is  less  than  that  of  the  earth  in  the 
proportion  of  about  twenty-five  to  sixty-four,  or,  more 
exactly  (and  more  conveniently),  the  surface  of  the 
earth  is  two  and  a  half  times  as  extensive  as  that  of 
Mars. 


loo  OTHER    WORLDS  THAN  OURS. 

The  substance  of  Mars  has  an  average  density 
rather  less  than  three-fourths  of  our  earth's,  or  very 
nearly  four  times  that  of  water.  Thus  gravity  at  his 
surface  is  much  less  than  terrestrial  gravity.  It  is,  in 
fact,  even  less  than  gravity  at  the  surface  of  Mercury, 
insomuch  that  one  of  our  pound  weights  placed  at  the 
surface  of  Mars  would  weigh  but  6  ozs.  3  dwts.,  in- 
stead of  nearly  seven  ounces  as  on  Mercury.  I  have 
already  dwelt  on  the  effects  of  such  a  relation  as  this, 
and  shall  have  occasion,  when  describing  the  habi- 
tudes of  Jupiter,  to  discuss  the  converse  relation.  But 
I  may  remark,  in  passing,  how  singular  it  is  that  we 
should  be  compelled  to  people  the  smallest  planets 
with  the  largest  inhabitants,  if  we  wish  to  bring  the 
inhabitants  of  different  orbs  to  about  the  same  scale 
of  activity.  A  Daniel  Lambert  on  Mars  would  be 
able  to  leap  easily  to  a  height  of  five  or  six  feet,  and 
he  could  run  faster  than  the  best  of  our  terrestrial 
athletes.  A  man  of  his  weight,  but  proportioned 
more  suitably  for  athletic  exercises,  could  leap  over  a 
twelve-feet  wall.  On  the  other  hand,  a  light  and  ac- 
tive stripling  removed  to  Jupiter  would  be  scarcely 
able  to  move  from  place  to  place.  On  the  sun  his 
own  weight  would  simply  crush  him  to  death. 

Mars  travels  in  an  orbit  of  considerable  eccen- 
tricity ;  in  fact,  the  centre  of  his  orbit  is  no  less  than 
thirteen  millions  of  miles  from  the  sun.  Accordingly, 
the  light  and  heat  he  receives  from  that  luminary 
vary  to  an  important  extent.  In  fact,  he  gets  about 
half  as  much  heat  and  light  again  when  in  perihelion 
as  when  in  aphelion.  This  circumstance  affects  to  an 


MARS,  THE  MINIATURE  OF  OUR  EARTH.       1Oi 

important  extent  the  climatic  relations  of  his  two 
hemispheres,  as  we  shall  presently  see. 

When  Mars  is  at  his  mean  distance  from  the  sun, 
the  light  and  heat  he  receives  are  less  than  ours  in  the 
proportion  of  about  four  to  nine.  The  length  of  his 
year  also  constitutes  a  noteworthy  circumstance  in 
which  his  habitudes  differ  from  those  of  our  earth. 
His  year  contains  very  nearly  six  hundred  and  eighty 
seven  of  our  days,  so  that  each  of  the  Martial  quarters 
lasts  about  five  and  two-thirds  of  our  months.  But, 
owing  to  the  eccentricity  of  his  orbit,  the  winter  and 
summer  of  the  northern  and  southern  hemispheres  are 
not  equal.  The  Martial  day  is  nearly  forty  minutes 
longer  than  ours.* 

His  equator  is  inclined  at  an  angle  of  about  twen- 
ty-seven and  a  quarter  degrees  to  the  plane  of  his 
orbit,  and  as  the  corresponding  inclination  in  the  case 
of  the  earth  is  about  twenty-three  and  a  half  de- 
grees, it  will  be  seen  that  his  seasonal  changes  do  not 
differ  much  in  character,  so  far  at  least  as  they  depend 
on  inclination,  from  our  own. 

The  axis  of  Mars  is  so  situated  that  the  summer 
of  his  northern  hemisphere  occurs  when  he  is  at  his 
greatest  distance  from  the  sun.  The  same  relation 
holds  in  the  case  of  the  earth,  the  sun  being  one  mill- 
ion five  hundred  thousand  miles  nearer  to  us  in  win- 
ter than  in  summer,  whereas,  to  those  who  live  in  the 

*  More  exactly,  the  length  of  the  Martial  day  is  24h.  37m.  22.735s. 
This  estimate  I  have  obtained  by  comparing  pictures  taken  by  Hookein 
1666,  and  by  Dawes  and  Browning  hi  1866-1869 — with  precautions 
sufficing  to  secure  that  no  complete  rotation  should  anywhere  be  lost 
sight  of. 


102  OTHER    WORLDS  THAN  OURS. 

southern  hemisphere,  he  approaches  nearer  in  summer 
than  in  winter.  But  the  effects  resulting  from  the 
relation  in  the  case  of  Mars  must  be  very  much  more 
striking  than  those  we  recognize.  For,  whereas  the 
sun  gives  only  one-fifteenth  more  heat  to  the  whole 
earth  in  January  than  he  does  in  July,  the  sun  of 
Mars  gives  half  as  much  light  again  in  perihelion  as 
in  aphelion.  The  summer  of  the  northern  hemisphere 
of  Mars  must  be  rendered  much  cooler  and  the  winter 
much  warmer  by  this  arrangement.  On  the  other 
hand,  the  contrast  between  the  summer  and  winter  of 
the  southern  hemisphere  is  rendered  more  striking 
than  it  otherwise  would  be. 

It  is,  however,  the  telescopic  aspect  of  Mars,  rather 
than  relations  such  as  we  have  been  dealing  with, 
that  affords  the  most  interesting  evidence  respecting 
the  fitness  of  the  planet  to  be  the  abode  of  living  crea- 
tures. Although  the  least  but  one  among  the  prima- 
ry planets — a  mere  speck  compared  with  Jupiter  and 
Saturn — Mars  has  been  examined  more  minutely  and 
under  more  favorable  circumstances  than  any  object 
in  the  heavens  except  the  moon.  He  does  not  ap- 
proach us  so  closely  as  Yenus,  nor  does  his  disk  ap- 
pear so  large  as  Jupiter's,  yet  he  is  seen  more  favor- 
ably than  the  former  planet,  and  on  a  larger  scale,  in 
reality,  than  the  latter.  In  fact,  whereas  Yenus  is 
one  of  the  most  unsatisfactory  of  all  telescopic  objects, 
Mars  is  one  of  the  most  pleasing  ;  and,  whereas  Jupi- 
ter is  always  more  than  three  hundred  and  eighty 
millions  of  miles  from  us,  Mars  sometimes  approaches 
us  within  less  than  forty  millions  of  miles. 


MARB,  THE  MINIATURE  OF  OUR  EARTH.       1O3 

Yet  even  tliis  distance  is  enormous,  and  it  affords 
high  evidence  of  the  skill  with  which  modern  tele- 
scopes are  constructed  and  used,  that  astronomers 
should  have  been  able  to  span  that  mighty  gulf,  and  to 
bring  from  beyond  it  reliable  information  respecting 
the  structure  of  so  distant  a  world. 

Such  information  has  been  brought,  however,  and 
is  full  of  interest. 

Yiewed  with  the  naked  eye,  the  most  remarkable 
feature  Mars  presents  is  his  ruddy  color.  In  the  tele- 
scope this  color  is  not  lost,  but,  instead  of  characteriz- 
ing the  whole  surface  of  the  planet,  it  is  confined  to 
particular  regions — the  intermediate  parts  being  for 
the  most  part  darker,  and  of  a  somewhat  greenish  hue. 
But  a  noteworthy  feature  adds  largely  to  the  beauty 
of  the  picture  presented  by  the  globe  of  Mars.  Two 
bright  spots  of  white  light  are  seen  on  opposite  sides 
of  his  disk,  presenting  precisely  such  an  appearance 
as  we  might  imagine  the  snowy  poles  of  our  earth  to 
exhibit  to  an  astronomer  on  the  planet  Yenus. 

Toward  the  edge  of  the  disk,  the  ruddy  and  the 
greenish  tracts  are  lost  in  a  misty  whiteness,  which 
grows  gradually  brighter  up  to  the  very  border  of  the 
planet.  We  shall  presently  see  that  this  peculiarity, 
rightly  understood,  is  one  of  the  most  instructive  fea- 
tures of  the  planet's  aspect. 

No  telescopist  has  yet  been  able  to  recognize  a 
satellite  attending  on  the  Planet  of  "War. 

It  was  discerned,  more  than  two  hundred  years  ago, 
that  the  reddish  spots  on  Mars,  and  the  darker  regions 
which  lie  between  them,  are  not  accidental  or  variable 


104  OTHER   WORLDS  THAN   OURS. 

phenomena,  but  represent  permanent  peculiarities  of 
the  Martial  surface.  Cassini,  with  one  of  those  outra- 
geously long  telescopes  which  were  used  before  the 
invention  of  achromatic  refractors,  was  the  first  to  dis- 
cover this.  But  the  ingenious  Hooke  seems  to  have 
obtained  better  views  of  Mars  in  1666.  At  least,  his 
pictures  of  the  planet  are  the  only  ones  taken  in  the 
seventeenth  century,  in  which  I  can  recognize  the 
now  well-known  aspect  of  the  Martial  continents  and 
oceans. 

Since  then,  Maraldi  and  the  Herschels,  Arago, 
Secchi,  Kunowski,  Beer,  and  Madler,  and  a  host  of 
other  eminent  astronomers,  have  not  thought  the  study 
of  the  planet's  aspect  beneath  their  notice.  Within 
the  last  few  years,  also,  this  work  has  been  prosecuted 
by  Nasmyth  and  Jacob,  Delarue  and  Phillips,  and 
finally  and  most  successfully  by  Lockyer  and  Dawes. 
The  last-named  observer,  especially,  whose  acuteness 
of  vision  earned  for  him  the  title  of  the  eagle-eyed, 
took  so  many  and  such  admirable  views  of  the  planet 
as  to  render  it  possible  to  form  a  globe  of  Mars.  Sir 
William  Herschel  had  charted  the  planet,  and  Messrs. 
Beer  and  Madler  had  made  improved  Martial  maps ; 
while  Prof.  Phillips,  from  observations  made  by  him- 
self and  Mr.  Lockyer,  had  constructed  two  globes  of 
Mars  in  which  many  features  were  presented.  But 
Mr.  Dawes's  pictures  of  the  planet  were  sufficient,  when 
carefully  compared,  for  the  formation  of  a  globe  in 
which  no  large  area  of  the  planet  should  be  left  bare  of 
details.  He  intrusted  to  me  no  less  than  twenty-seven 
drawings  of  Mars,  the  choicest  specimens  of  a  very 


1865  Jan.  I  7h  45' 


1864  Nov  20 . 


1864  Nov  I0l2h6m 


1864.NOV23  12h24r 


"THE    PLANET  MARS 


CO 

OC 


MARS,  THE  MINIATURE  OF  OUR  EARTH.       ^5 

iarge  series,  tliat  I  might  chart  the  planet  from  them. 
Four  of  his  drawings  are  shown  in  the  accompanying 
plate.  They  are  so  selected,  that  the  features  just 
coming  into  view  in  one  are  just  passing  away  in  the 
next.  The  accompanying  chart  of  Mars,  in  which  the 
darker  parts  of  the  planet  are  assumed  to  be  seas,  and 
the  reddish  tracts  continents,  exhibits  the  results  ob- 
tained from  the  study  of  the  complete  series.  This 
chart  is  on  the  stereographic  projection,  and  is  inverted 
— the  south  polar  regions,  that  is,  are  at  the  top — be- 
cause the  telescopes  commonly  used  by  observers  ex- 
hibit inverted  views  of  the  celestial  objects.*  At  the 
top  of  the  map  we  see  the  icy  region  which  lies  at  the 
southern  pole  of  Mars.  Around  that  region  is  a  sea  un- 
named in  the  map.  Then  along  the  southern  temperate 
zone  there  lie  several  tracts  of  Martial  land,  named 
after  Cassini,  Lockyer,  and  other  astronomers.  These 
regions  appear  to  form  a  continuous  land-belt  round 
the  temperate  zone ;  though  there  is  some  uncertainty 
on  this  point,  owing  to  the  fact  that  the  coast-line  is 
not  often  very  distinctly  visible.  We  now  approach, 
however,  a  part  of  the  map  where  all  the  features  are 
thoroughly  recognized  and  permanent.  Next  to  the 
circle  of  land  just  described,  there  is  a  nearly  complete 
circle  of  water,  one  strip  only  of  land  connecting  the 
equatorial  continents  of  Mars  with  the  south-temperate 
zone  of  minor  continents.  Beginning  at  the  eastern 
or  left-hand  extremity  of  the  map,  we  have  a  long  sea, 

*  Mr.  Browning,  F.  R.  A.  S.,  has  formed  a  globe  of  Mars  from  my 
chart,  and  publishes  an  interesting  series  of  photographs  of  this  globe 
which  give  fine  stereoscopic  effects. 


106  OTHER    WORLDS  THAN  OURS. 

called  Maraldi  Sea,  parallel  to  which  runs  Hooke  Sea, 
trending  in  a  northwesterly  direction,  and  so  running 
into  Dawes  Ocean;  still  farther  west  are  two  vast 
islands,  called  Jacob  Island  and  Phillips  Island,  be- 
tween which  runs  Arago  Strait.  Beyond  these  islands 
lies  Delarue  Ocean,  communicating  by  narrow  straits 
with  two  strikingly  similar  seas.  Here  the  zone  of 
water  ends,  and  we  have  only  to  note  further,  respect- 
ing it,  that  in  Delarue  Ocean  there  is  a  large  island, 
which  presents  so  strikingly  brilliant  an  aspect  that  it 
has  been  supposed  to  be  covered  (ordinarily)  with 
snow.  It  has  been  called  Dawes's  Ice  Island. 

I  now  come  to  the  most  remarkable  feature  of  the 
Martial  geography — or  perhaps  I  ought  rather  to  say, 
areography.  This  is  the  great  equatorial  zone  of 
continents.  There  are  four  of  these.  On  the  left  of 
the  map  is  Herschel  I.  Continent.  Next  is  Dawes 
Continent,  the  largest  of  the  four,  and  separated  from 
the  former  by  a  long  sea  called  Kaiser  Sea.  This  sea 
is  one  of  the  most  striking  marks  on  the  planet,  and 
has  been  recognized  from  the  earliest  days  of  telescopic 
observation.  It  is  connected  toward  the  east  with  a 
flask-shaped  sea,  somewhat  resembling  the  two  which 
lie  at  the  western  extremity  of  the  zone  of  water  just 
described.  At  its  northernmost  end  it  turns  sharply 
westward,  and  forms  the  southern  boundary  of  Dawes 
Continent.  Fartlier  west  lies  Madler  Continent,  sepa- 
rated from  Dawes  Continent  by  a  long  strait,  which 
runs  almost  directly  north  and  south.  Lastly,  there  is 
Secchi  Continent,  separated  from  Madler  Continent 
by  Bessel  Inlet  and  from  Herschel  Continent  by 


MARS,  THE  MINIATURE  OF  OUR  EARTH.       1O7 

Huggins  Inlet.  A  large  lake  on  the  last-named  con- 
tinent is  worthy  of  notice  on  account  of  its  singular 
shape.  It  consists  of  two  bell-shaped  seas  connected 
by  a  narrow  and  sharply-curved  strait. 

The  northern  half  of  Mars  has  not  been  so  thor- 
oughly examined  as  the  southern,  for  a  reason  which 
will  presently  be  mentioned.  It  is  known,  however, 
that,  in  all  essential  respects,  it  resembles  the  southern 
hemisphere.  Next  to  the  equatorial  zone  of  continents 
there  comes  a  zone  of  water,  expanding  at  one  point 
into  Beer  Sea,  and  at  another  into  Tycho  Sea.  Then 
comes  a  zone  of  land,  called  Laplace  Land,  in  which 
lies  an  enormous  lake  called  Delambre  Sea.  Next  is 
a  narrow  zone  of  water  called  the  Schroter  Sea,  and 
so  we  reach  the  north-polar  ice-cap. 

I  have  been  speaking  of  the  spots  on  Mars  as  though 
they  undoubtedly  represented  land  and  water.  But 
many  may  be  disposed  to  question  the  evidence  we 
have  on  this  point — to  ask  why  the  ruddy  spots  should 
be  held  to  be  continents  or  islands,  and  the  greenish- 
colored  markings  to  be  oceans,  seas,  and  lakes.  We 
know  that,  for  a  long  time  after  the  invention  of  the 
telescope,  astronomers  called  the  darker  portions  of  the 
moon,  seas.  They  spoke  of  the  Sea  of  Serenity,  the 
Sea  of  Crises,  the  Sea  of  Humors,  and  so  on,  and  we 
now  know  for  certain  that  these  dusky  regions  are  not 
seas.  It  may  be  asked,  therefore,  how  we  can  feel 
certain  that  the  dark  spots  on  Mars  are  oceans. 

At  first  sight,  this  question  seems  a  difficult  one 
to  answer.  The  most  powerful  telescopes  have  been 
directed  toward  the  moon,  without  affording  any  sat* 


108  OTHER   WORLDS  THAN  OURS. 

isfactory  information  respecting  the  condition  of  ita 
surface.  Mars,  therefore,  which  lies — even  under  the 
most  favorable  circumstances — more  than  one  hundred 
and  sixty  times  farther  from  us  than  the  moon,  might 
be  thought  to  be  altogether  beyond  the  reach  of  our 
telescopists — so  far,  at  least,  as  any  knowledge  of  the 
Martial  surface  is  concerned.  But  one  important  dis- 
tinction between  Mars  and  the  moon  must  be  careful- 
ly attended  to.  The  surface  of  the  moon  is  always  the 
same — no  natural  processes  seem  ever  to  take  place 
over  that  scene  of  desolation,  though  the  moon  is  ex- 
posed to  contrasts  of  temperature,  compared  with 
which  the  distinction  between  the  intensest  heat  of 
our  summers  and  the  bitterest  cold  of  our  winters 
seems  altogether  evanescent.  But,  on  Mars,  the  case 
is  certainly  different.  Whatever  opinion  we  may 
form  respecting  Martial  habitudes,  whether  we  assume 
or  not  that  Mars  is  the  abode  of  any  forms  of  animal 
life,  there  can  be  no  question  whatever  that  physical 
processes  of  change  are  taking  place  on  a  grand  scale 
in  that  distant  world.  Many  evidences  of  this  can  be 
at  once  adduced.  We  have  spoken  of  the  Martial  fea- 
tures as  constant.  They  differ,  for  instance,  from  the 
markings  on  Jupiter,  which  are  as  changeful  as  the 
aspect  of  our  April  skies.  But  though  the  same  mark- 
ing may  have  been  seen  by  Hooke  in  1666,  by  Maral- 
di  in  1720,  by  Herschel  in  1780,  by  Beer  and  Madler 
in  1830-'37,  and  by  Dawes  in  1852-'65,  yet  it  by  no 
means  follows  that  it  is  always  visible  when  the  part 
of  Mars  to  which  it  belongs  is  turned  toward  us.  A 
veil  is  sometimes  drawn  over  it  for  hours  or  even  days 


MARS,  THE  MINIATURE  OF  OUR  EARTH.       1O9 

together.  And  this  veil  has  nothing  to  do  with  the 
distinctness  or  indistinctness  with  which  our  own  at- 
mosphere permits  us  to  see  the  planet.  A  spot  will 
be  blurred  and  indistinct  when  a  neighboring  marking 
is  exhibited  with  unusual  clearness. 

Let  us  consider  an  instance  of  this  peculiarity.  On 
October  3,  1862,  Mr.  Lockyer  was  observing  Mars 
late  in  the  evening.  He  noticed  that  a  part  of  Dawes 
Ocean,  where  it  borders  on  Herschel  Continent,  was 
hidden  from  view.  In  place  of  the  ordinarily  dark 
aspect  of  this  region,  a  faint,  misty  light,  with  ill-de- 
fined borders,  was  observable.  As  the  evening  pro- 
gressed, he  noticed  that  the  outlines  gradually  became 
clearer,  but,  when  he  gave  up  observation  (at  about 
half-past  eleven),  the  white  light  still  continued  to 
veil  the  outline  of  a  part  of  Dawes  Ocean.  Now,  Mr. 
Dawes  observed  Mars  on  the  same  night,  at  a  quarter- 
past  twelve.  The  drawing  which  he  took  at  that 
hour  shows  that  the  process  of  clearing  up,  noticed  by 
Mr.  Lockyer  as  being  in  progress  in  the  earlier  part 
of  the  night,  had,  by  the  time  Mr.  Dawes  began  work, 
entirely  lifted  off  the  veil  which  concealed  the  coast- 
line. The  remains  of  the  misty  light  seen  by  Lockyer 
are  still  to  be  detected  in  Mr.  Dawes's  drawing,  but 
they  have  passed  farther  south,  and  no  longer  hide 
the  shores  of  Dawes  Ocean. 

The  Padre  Secchi,  of  the  Collegio  Romano,  states 
that  he  has  often  noticed  similar  appearances,  while 
observing  Mars  with  the  fine  refractor  in  the  observa- 
tory of  that  institution. 

But  yet  another  peculiarity  of  the  same  sort  re 


,10  OTHER    WORLDS  THAN  OURS. 

mains  to  be  mentioned.  Mars,  as  I  have  said,  has  his 
winter  and  summer  seasons.  Since  we  know  the  po- 
sition of  the  Martial  equator  upon  his  surface,  we  can 
tell  what  season  is  in  progress  in  either  hemisphere  at 
any  given  time.  Now,  it  has  been  noticed  that,  when 
it  is  winter  in  one  hemisphere,  and  therefore  summer 
in  the  other,  the  former  hemisphere  is  nearly  always 
hidden  from  view  by  just  such  a  veil  as  I  have  spoken 
of  above. 

I  may  remark,  in  passing,  that  this  peculiarity  has 
led  many  observers  to  form  very  erroneous  impressions 
respecting  the  distribution  of  land  and  water  over  the 
surface  of  Mars.  Seeing  one  hemisphere  covered  for 
weeks  together  with  whitish  light,  they  have  con- 
cluded that  there  are  no  oceans  there ;  and  if  they 
have  no  other  opportunity  of  observing  the  planet, 
the  mistaken  impression  remains,  and  is  published  to 
the  world  with  all  the  authority  of  the  observer's  name. 

Now,  what  is  this  veil  which,  sometimes  for  a  few 
hours  or  days,  at  others  for  months  together,  is  drawn 
over  the  features  of  the  Martial  globe  ?  Have  we  any 
terrestrial  analogies,  by  means  of  which  we  may  in- 
terpret this  phenomenon  ? 

To  answer  these  questions,  let  us  conceive  the 
case  of  an  observer  on  Yenus,  watching  our  earth. 
Would  such  an  observer  always  see  the  features  of 
this  globe  with  equal  distinctness?  When  heavy 
masses  of  cloud  are  drawn  over  a  wide  expanse  of 
country — spreading  often,  as  meteorologists  record, 
for  hundreds  and  even  thousands  of  miles — can  we 
suppose  that  the  astronomer  on  Yenus  could  pierco 


MARS,  THE  MINIATURE  OF  OUR  EARTH.       m 

through  the  veil?  Since  we  cannot  see  the  bright 
body  of  the  sun  through  a  dense  cloud-veil,  we  may 
be  certain  that  the  observer  on  Yen  us  cannot  see  the 
oceans  and  continents  of  our  earth  when  thus  cloud- 
shadowed.  So  far  as  the  cloud-veil  extends,  the  lands 
and  seas  of  this  globe  would  be  to  him,  at  such  a  time, 
as  though  they  were  not. 

Here,  then,  we  have  an  argument  from  analogy 
for  supposing  that  the  veil,  which  from  time  to  time 
conceals  the  Martial  features,  may  resemble  terres- 
trial cloud-banks.  Let  us  next  inquire  whether  there 
is  any  thing  in  the  behavior  of  the  Martial  veil  to 
justify  this  view. 

It  is  clear  that,  if  we  held  the  concealing  medium 
to  be  of  a  cloudy  nature,  the  disappearance  of  the  fea- 
tures of  the  hemisphere  which  is  passing  through  the 
Martial  winter  would  indicate  that  in  winter  the 
Martial  skies  are  more  clouded  than  in  summer.  "We 
know  that  this  is  the  case  on  our  own  earth — that 
fogs  and  mists,  clouds,  rain,  and  snow,  are  phenomena 
far  more  frequently  observed  in  winter  than  in  sum- 
mer. "We  know  also  why  it  is  so.  The  cold  winter 
air  is  unable  to  retain  the  aqueous  vapor  continually 
passing  into  it,  and  is  thus  forced  to  precipitate  this 
vapor  in  one  or  other  of  the  forms  just  named.  Nor 
can  we  see  any  reason  why  the  Martial  atmosphere, 
supposing  it  to  resemble  our  own,  should  not  act  in 
precisely  the  same  manner.  Thus  we  recognize,  in 
the  remarkable  seasonal  peculiarity  above  described, 
what  seems  to  be  the  exact  counterpart  of  processes 
recognized  upon  the  earth. 


112  OTHER   WORLDS  THAN  OURS. 

And  though  I  admit  that  there  is  considerable  ob- 
jection to  the  mode  of  argument  I  am  next  going  to 
make  use  of,  yet,  as  it  is  one  which  has  great  weight 
with  many  minds,  and  is  not  without  its  own  peculiar 
force,  I  feel  justified  in  applying  it  as  a  subsidiary 
support  to  the  views  I  am  discussing.  It  is  known 
that  the  peculiarities  which  characterize  terrestrial  at- 
mospheric phenomena  tend  in  an  important  manner 
to  mitigate  the  extremes  of  summer  and  winter  tem- 
perature. The  clouds  which  hang  over  our  winter 
skies,  far  from  acting  to  increase  the  coldness  of  win- 
ter through  their  effect  in  keeping  off  the  sun's  rays, 
in  reality  represent  an  enormous  supply  of  heat 
brought  from  warmer  parts  of  the  earth,  and  liberated 
for  our  benefit  as  the  invisible  vapor  of  water  assumes 
the  form  of  cloud  or  rain.  And  although  these  pro- 
cesses are  strictly  in  accordance  with  natural  laws,  yet 
we  are  justified  in  recognizing  them  as  evidences  of 
the  beneficence  of  the  Almighty.  Now,  on  Mars,  we 
may  be  sure,  the  winters  tend  to  be  far  more  bitter 
than  ours,  partly  because  of  his  greater  distance  from 
the  sun,  but  chiefly  because  of  the  more  marked  con- 
trast existing  between  his  various  seasons.  Hence,  if 
there  are  living  creatures  on  Mars,  it  can  scarcely  be 
doubted  that  an  arrangement  such  as  that  which  pre- 
vails on  earth  is  yet  more  necessary  to  the  welfare  of 
the  Martialists.  Thus,  we  derive  an  argument  from 
the  a  priori  consideration  of  the  nature  of  Martial 
requirements,  to  favor  our  interpretation  of  the  phe- 
nomena actually  observed. 

Perhaps  the  reader  may  be   disposed  to   inquire 


MARS,  THE  MINIATURE  OF  OUR  EARTH.       113 

whether  the  clearing  up  of  a  portion  of  the  Martial 
disk  observed  by  Lockyer  and  Dawes  admits  of  inter- 
pretation in  a  similar  way.  To  this  it  may  be  replied 
that,  from  the  observed  position  of  the  region  in  ques- 
tion, the  Martial  time  of  day  there  must  have  been 
somewhere  about  noon  when  Mr.  Lockyer  began  hia 
observations,  and  about  one  o'clock  in  the  afternoon 
(according  to  our  terrestrial  mode  of  reckoning)  when 
Mr.  Dawes  observed  the  planet.  It  is  no  uncommon 
thing  to  see  our  terrestrial  skies  clear  up  soon  aftei 
midday;  and  if  the  veil  which  conceals  the  Martial 
features  is  really  cloudy,  this  is  precisely  what  hap- 
pened out  yonder,  forty  millions  of  miles  away  from 
us,  on  the  day  in  question. 

I  think  the  reader  will  at  least  concede  that  the 
explanation  here  given  of  these  peculiarities  is  more 
natural  than  one  which  was  put  forward  some  time 
since  by  an  eminent  French  astronomer.  He  urged 
that  Martial  vegetation,  instead  of  being  green  like 
ours,  is  red ;  hence  in  the  Martial  summer  the  sur- 
face, as  seen  by  us,  assumes  a  ruddy  aspect,  while  the 
wintry  hemisphere  loses  its  ruddy  tint.  According  to 
this  interpretation,  such  changes  as  were  noticed  by 
Secchi  would  indicate  the  sudden  blooming  forth  of 
Martial  vegetation  over  hundreds  of  square  miles  of 
the  Martial  surface. 

To  the  evidence  already  dealt  with  may  be  added 
that  which  is  afforded  by  the  whiteness  of  the  disk  of 
Mars  near  the  edge.  Knowing  that  the  parts  of 
Mars  which  thus  appear  concealed  in  mist  are  those 
where  it  is  morning  or  evening  to  the  Martialists,  we 


,14  OTHER   WORLDS  THAN  OURS. 

see  a  close  analogy  here  to  terrestrial  relations,  since 
our  own  skies  are  commonly  more  moisture-laden  in 
the  morning  and  evening  than  near  midday.* 

I  may  here  pause,  in  passing,  to  notice  under  what 
difficulties  the  observation  of  Mars  is  conducted  by 
the  terrestrial  observer.  To  begin  with,  the  sky  must 
be  exceptionally  clear;  and  none  but  the  practised 
observer  knows  how  seldom  there  occurs  what  is 
called  "  a  good  observing  night."  Then  it  must  be  a 
fine  day  for  the  Martialists,  for  clouds  over  Mars,  or 
even  an  imperfectly  clear  atmosphere,  must  produce 
quite  as  bad  an  effect  in  spoiling  the  definition  of 
Martial  features  as  similar  phenomena  on  earth. 
Again,  Mars  only  comes  into  a  favorable  position 
once  in  every  two  and  a  quarter  years,  continuing  to 
be  well  placed  for  only  a  few  months.  Thus  it  hap- 
pens that,  although  Mars  has  been  telescopically  ob- 
served for  more  than  two  hundred  years,  the  actual 
time  during  which  he  has  been  favorably  placed  for 
observation  has  been  very  much  less ;  and,  taking  into 
account  all  the  requirements  for  good  definition,  it 
may  be  said  that  Mars  has  not  been  under  really  ef- 
fective observation  for  more  than  a  very  few  days. 

Of  course,  if  we  admit  that  the  vaporous  envelope 


*  In  the  Popular  Science  Review  for  January,  1869,  1  have  indi- 
cated a  subsidiary  explanation  of  this  peculiarity,  founded  on  the  prob- 
able shape  of  the  Martial  clouds.  For  the  same  reason  that,  near  the 
horizon,  our  own  cumulus  clouds  seem  more  closely  packed  than  over- 
head, the  Martialists  would  see  a  clearer  sky  overhead  than  near  the 
horizon.  It  follows,  at  once,  that  we  should  see  those  parts  of  the  sur- 
face of  Mars  best  which  we  look  upon  in  a  nearly  vertical  direction, 
that  is,  the  central  parts  of  his  disk. 


MARS,  THE  MINIATURE  OF  OUR  EARTH       115 

which  occasionally  hides  parts  of  Mars  is  aqueous,  we 
must  believe  in  the  existence  of  oceans  upon  Mars. 
And,  from  our  knowledge  of  the  appearance  of  our 
own  seas,  we  should  immediately  recognize  the  green- 
ish parts  of  Mars  as  the  Martial  oceans,  and  look  upon 
the  ruddy  parts  as  continents.  We  have  seen  that 
the  behavior  of  the  vaporous  envelopes  corresponds  to 
that  of  our  own  clouds  and  fogs.  But  it  might  be 
thought  possible  that  the  vapors  arise  from  fluids 
other  than  water ;  that,  in  fact,  a  state  of  things  ex- 
ists upon  Mars  wholly  different  from  that  which  pre- 
vails upon  our  own  earth. 

Ten  years  ago  it  would  have  been  very  difficult  to 
disprove  such  an  argument  as  this,  however  bizarre  it 
may  seem.  But  the  wonderful  powers  of  the  spectro- 
scope have  been  applied  to  this  question,  and  there  is 
no  mistaking  the  results  which  have  been  obtained. 
We  must  premise  that  this  is  hardly  a  favorable  case 
for  the  application  of  spectroscopic  analysis,  which  (as 
available  to  the  astronomer)  deals  most  effectively 
with  self-luminous  objects.  Still,  there  was  a  possibil- 
ity that  the  light  which  comes  from  Mars  might  have 
been  so  acted  upon  by  vapors  in  the  Martial  atmos- 
phere, that  its  spectrum  would  be  affected  in  an  ap- 
preciable manner. 

Mr.  Huggins  examined  Mars  in  1864  without  satis- 
factory results,  but  at  the  opposition  of  Mars  in  1867  hr 
was  more  successful.  In  the  following  description  ol 
his  most  striking  observation  I  epitomize  his  account : 
On  February  14th  he  examined  Mars  with  a  spectro- 
scope attached  to  his  powerful  eight-inch  refractor, 


n6  OTHER    WORLDS  THAN  OURS. 

The  rainbow-colored  streak  was  crossed,  near  the  or- 
ange part,  by  groups  of  dark  lines  agreeing  in  posi- 
tion "  with  ]ines  which  make  their  appearance  in  the 
solar  spectrum  when  the  sun  is  low  down,  so  that  its 
light  has  to  traverse  the  denser  strata  of  our  atmos- 
phere." To  determine  whether  these  lines  belonged 
to  the  light  from  Mars  or  were  caused  by  our  own  at- 
mosphere, Mr.  Huggins  turned  his  spectroscope  tow- 
ard the  moon,  which  happened  to  be  nearer  the  hori- 
zon than  Mars,  so  that  the  atmospheric  lines  would  be 
stronger  in  the  moon's  spectrum  than  in  that  of  the 
planet.  But  the  group  of  lines  referred  to  was  not 
visible  in  the  lunar  spectrum.  Hence  it  was  clear  that 
they  belong  to  the  Martial  atmosphere,  and  not  to 
ours. 

I  have  said  that  these  lines  appear  in  the  solar 
spectrum  when  the  sun  is  shining  through  the  denser 
strata  of  our  atmosphere.  Let  us  consider  a  moment 
the  light  which  this  fact  throws  on  the  nature  of  the 
Martial  atmosphere.  It  must  contain  at  least  those 
constituent  vapors  whose  existence  in  our  atmosphere 
causes  the  appearance  of  these  lines  in  the  solar  spec 
trum.  Hence  there  must  be  some  similarity  between 
the  Martial  atmosphere  and  our  own.  But  we  know 
from  the  researches  of  the  Padre  Secchi,  that  it  is  the 
aqueous  vapor  in  our  air  which  causes  the  appearance 
of  the  lines  in  question.  Hence  there  must  be  aqueous 
vapor  in  the  Martial  atmosphere. 

This  discovery  at  once  justifies  the  title  of  the 
present  chapter.  Let  us  consider  what  a  number  of 
interesting  results  follow  from  it. 


MAR8,  THE  MINIATURE  OF  OUR  EARTH.       117 

The  water  in  the  Martial  air  must  be  raised  from 
seas  and  rivers  upon  the  planet.  These,  therefore, 
consist  of  water  and  not  of  other  fluids.  The  two 
white  spots,  then,  on  the  Martial  disk  are  no  longer 
doubtful  appearances.  Before  the  discovery  that  water 
exists  on  Mars,  it  was  perhaps  somewhat  bold  to  pro- 
nounce that  these  spots  certainly  indicate  the  presence 
of  ice-fields  around  the  Martial  poles,  resembling  those 
which  exist  around  the  poles  of  the  earth.  Sir  Wil- 
liam Herschel,  indeed,  with  that  confidence  which  he 
always  showed  when  he  had  a  trustworthy  analogy  to 
guide  him,  came  to  this  conclusion  on  the  strength  of 
the  correspondence  between  the  changes  of  the  two 
spots  and  the  progress  of  the  Martial  seasons.  But 
many  astronomers  felt  that  there  was  still  room  to 
doubt  whether  we  could  really  speak  of  the  spots  as 

"  The  snowy  poles  of  moonless  Mars." 

Now,  however,  we  know  that  they  can  be  no  other 
than  snow-caps.  Kay,  if  Mars  were  so  far  off  that  we 
could  not  distinguish  these  spots,  we  could  yet,  on  the 
strength  of  what  the  spectroscope  has  taught  us,  pro- 
nounce confidently  that  his  polar  regions  must  be  ice- 
bound. 

Let  us  proceed  a  step  or  two  farther.  We  have 
Been  that  there  are  oceans  on  Mars ;  we  know  that 
clouds  and  vapors  rise  from  those  oceans  and  are 
wafted  over  his  continents ;  and,  finally,  we  have 
learned  that  snow  falls  on  the  Martial  polar  regions. 
These  things  are  very  interesting  in  themselves,  but 
they  indicate  the  occurrence  of  processes  yet  more  in- 


;i8  OTHER    WORLDS  THAN  OURS. 

teresting.  The  formation  and  the  dissipation  of  clouds 
are  among  the  most  important  of  all  the  processes  by 
which  Nature  arranges  and  modifies  the  temperature 
of  our  earth.  The  heat  of  the  sun's  rays  is  used  up, 
BO  to  speak,  in  raising  aqueous  vapor  from  the  surface 
of  the  ocean.  Thus  the  air  is  rendered  cooler  than  it 
otherwise  would  be,  and  this  takes  place  just  where 
coolness  is  most  needed.  But  the  aqueous  vapor,  once 
raised,  is  swept  by  the  winds  to  other  regions.  So 
long  as  the  air  remains  warm,  the  aqueous  vapor  re- 
mains unchanged  ;  but,  so  soon  as  it  has  been  carried 
to  colder  regions,  it  is  condensed  into  the  form  of  cloud 
or  mist,  and  while  changing  to  this  form  it  parts  with 
the  heat  which  had  turned  it  into  vapor.  Thus  where 
heat  is  in  excess,  it  is  used  up  in  forming  aqueous 
vapor,  and  where  heat  is  wanted  there  the  aqueous 
vapor  distributes  it. 

We  see,  then,  that  on  Mars  there  exists  the  same 
admirable  contrivance  for  tempering  climates  which 
we  find  on  our  own  earth. 

But  let  us  consider  yet  another  office  fulfilled  by 
aqueous  vapor.  It  not  only  serves  to  convey  the  heat 
from  the  warmer  parts  of  the  earth  to  those  regions 
where  heat  is  most  needed.  It  forms  clouds  which 
serve  to  shelter  the  earth  from  the  sun's  heat  by  day, 
and  to  prevent  the  escape  of  the  earth's  heat  by  night, 
which  also,  in  refreshing  rains,  "  drop  fatness  on  the 
earth."  Now,  the  clouds  on  Mars  are  certainly  dissi- 
pated in  some  way,  because,  as  I  have  said,  astronomers 
have  repeatedly  seen  them  disappear.  And  doubtless, 
like  our  own  clouds,  they  are  often  dissipated  by  the 


MARS,  THE  MINIATURE  OF  OUR  EARTH.       119 

sun's  heat.  But  we  may  take  it  for  granted  that,  like 
our  terrestrial  clouds,  they  are  also  often  dissipated  by 
falling  in  rain.  Thus  the  Martial  lands  are  nourished 
by  refreshing  rainfalls ;  and  who  can  doubt  that  they 
are  thus  nourished  for  the  same  purpose  as  our  own 
fields  and  forests — namely,  that  vegetation  of  all  sorts 
may  grow  abundantly  ? 

But  yet,  again,  the  transit  of  clouds  from  place  to 
place  implies  the  existence  of  aerial  currents.  Clouds 
cannot,  indeed,  even  form  and  be  dissipated  without 
occasioning  wind-currents ;  and  it  need  hardly  be  said 
that  the  Martial  clouds  could  not  be  carried  to  his 
polar  regions,  there  to  fall  in  snow,  unless  the  atmos- 
pheric currents  on  Mars  were  extensive  and  persist- 
ent. We  see,  then,  that  Mars  has  winds  as  our  earth 
has.  Doubtless  his  trade-winds  are  less  marked  than 
ours,  because  his  surface  rotates  less  rapidly  than  the 
earth's,  his  globe  being  much  smaller,  while  his  rota- 
tion-period is  slightly  greater.  But  he  has  less  need 
for  trade-winds,  his  oceans  being  so  much  less  exten- 
sive than  ours.  No  Columbus  on  Mars  has  ever 
needed  the  persistent  breath  of  easterly  winds  to  en- 
courage him  on  his  voyage  to  an  undiscovered  conti- 
nent. Bather,  the  intricate  navigation  of  the  narrow 
Martial  seas  would  be  favored  by  variable  breezes. 
But  the  great  purposes  which  the  circulation  of  our 
own  atmosphere  subserves  are  carried  out  efficiently 
out  yonder  on  Mars.  The  air  is  cleansed  and  purified, 
its  thermal  and  electrical  conditions  are  regulated, 
clouds  are  wafted  from  place  to  place ;  and,  in  fine, 
the  atmosphere  is  rendered  fit  for  all  those  pur- 


120  OTHER    WORLDS  THAN  OURS. 

poses  for  which,  like  our  own,  it  has  doubtless  been 
created. 

"We  may  trace  yet  further,  however,  the  results 
which  flow  from  the  existence  of  aqueous  vapor  in 
the  atmosphere  of  Mars.  We  see  the  polar  snows 
aggregating  in  the  Martial  winter  and  diminishing  in 
the  Martial  summer.  And  we  know  that,  on  our  own 
earth,  the  increase  and  the  diminution  of  the  polar 
snows  are  processes  intimately  associated  with  the 
formation  and  maintenance  of  the  oceanic  circulation. 
Doubtless  much  yet  remains  to  be  done  before  that 
system  of  circulation  will  be  fully  understood.  The 
rival  views  which  have  been  maintained  by  Sir  John 
Herschel  and  Captain  Maury  have  served  to  throw  a 
certain  air  of  doubt  over  the  theory  of  ocean-currents.* 
But  whether  we  ascribe  the  equatorial  currents  of  our 
oceans  to  the  trade-winds  with  Herschel,  or  to  differ- 
ences of  specific  gravity  with  Maury,  we  see  that,  in 
the  first  place,  both  causes  operate  in  the  case  of  Mars, 
and  secondly,  that  the  submarine  return -currents  from 

*  If  Herschel  has  completely  overthrown  Maury's  theory  that  currents 
are  altogether  due  to  differences  of  specific  gravity,  saltness,  and  so  on, 
Maury  has  at  least  been  as  successful  in  overthrowing  Herschel's  theory 
that  the  currents  are  due  to  the  trade-winds.  A  theory  more  probable 
than  either  is,  I  think,  that  according  to  which  the  whole  system  of 
circulation  is  set  in  motion  by  the  continual  evaporation  going  on  in 
equatorial  seas.  Thus,  by  a  process  resembling  suction,  an  in-draught 
of  cold  water  is  caused,  and  this  water  coming  from  higher  latitudes, 
where  the  earth's  eastwardly  motion  is  less,  to  lower  latitudes,  where  the 
eastwardly  motion  is  greater,  produces  the  relatively  cold  and  westwardly 
equatorial  currents  which  exist  in  the  Atlantic,  Indian,  and  Pacific 
Oceans.  Recent  reseat  ches  into  the  temperature  of  the  deep  sea  have 
tended  strongly  to  confirm  these  views,  which  I  dealt  with  at  some 
length  in  the  Intellectual  Observer  for  May,  1867. 


MARS,  THE  MINIATURE  OF  OUR  EARTH.       12i 

our  polar  regions  must,  at  any  rate,  be  due  to  the 
presence  of  ice  in  the  polar  seas.  So  that  undoubtedly 
the  Martial  oceans,  so  far  as  their  peculiar  conforma- 
tion will  permit,  are  traversed  by  currents  in  various 
directions  and  at  various  depths. 

Then,  lastly,  there  must  be  rivers  on  Mars.  The 
clouds  which  often  hide  from  our  view  the  larger  part 
of  a  Martial  continent,  indicate  a  rainfall  at  least  as 
considerable  (in  proportion)  as  that  which  we  have  on 
the  earth.  The  water  thus  precipitated  on  the  Martial 
continents  can  find  its  way  no  otherwise  to  the  ocean 
than  along  river-courses. 

As  to  the  nature  of  these  rivers  again,  we  may  form 
conjectures  founded  on  trustworthy  analogies.  The 
mere  existence  of  continents  and  oceans  on  Mars 
proves  the  action  of  forces  of  upheaval  and  of  depres- 
sion. There  must  be  volcanic  eruptions  and  earth- 
quakes, modelling  and  remodelling  the  crust  of  Mars. 
Thus  there  must  be  mountains  and  hills,  valleys  and 
ravines,  water-sheds  and  water-courses.  All  the  various 
kinds  of  scenery  which  make  our  earth  so  beautiful 
have  their  representatives  in  the  ruddy  planet.  The 
river  courses  to  the  ocean,  by  cataract  and  lake,  here 
urging  its  way  impetuously  over  rocks  and  bowlders, 
there  gliding  with  stately  flow  along  its  more  level 
reaches.  The  rivulet  speeds  to  the  river,  the  brook 
to  the  rivulet,  and  from  the  mountain  recesses  burst 
forth  the  refreshing  springs  which  are  to  feed  the 
Martial  brooklets. 

"Who  can  doubt  what  the  lesson  is  that  all  these 
things  are  meant  to  teach  us  ?  So  far,  let  it  be  re- 


122  OTHER   WORLDS  THAN  OURS. 

membered,  we  have  been  guided  onward  by  no  specu- 
lative fancies,  but  simply  by  sober  reasoning.  But 
can  we  pause  just  here  ?  Shall  we  recognize  in  Mars 
all  that  makes  our  own  world  so  well  fitted  to  our 
wants — land  and  water,  mountain  and  valley,  cloud 
and  sunshine,  rain,  and  ice,  and  snow,  rivers  and  lakes, 
ocean-currents  and  wind-currents,  without  believing 
further  in  the  existence  of  those  forms  of  life  without 
which  all  these  things  would  be  wasted  ?  Surely,  if 
it  is  rashly  speculative  to  say  of  this  charming  planet 
that  it  is  the  abode  of  life — if  we  must,  indeed,  limit 
ourselves  to  the  consideration  of  what  has  been  abso- 
lutely seen — it  is  yet  to  speculate  ten  thousand  times 
more  rashly  to  assert,  in  the  face  of  so  many  probable 
arguments  to  the  contrary,  that  Mars  is  a  barren 
waste,  either  wholly  untenanted  by  living  creatures,  or 
inhabited  by  beings  belonging  to  the  lowest  orders  of 
animated  existence. 


CHAPTER  Y. 

JUPITER,    THE    GIANT   OF   THE   SOLAS    SYSTIM. 

PASSING  over  the  zone  of  asteroids,  we  come  now 
tc  the  noblest  of  all  the  planets — the  giant  Jupiter.  If 
bulk  is  to  be  the  measure  of  a  planet's  fitness  to  be 
the  abode  of  living  creatures,  then  must  Jupiter  be 
inhabited  by  the  most  favored  races  existing  through- 
out the  whole  range  of  the  solar  system.  Exceeding  our 
earth  some  twelve  hundred  and  thirty  times  in  volume, 
and  more  than  three  hundred  times  in  mass,  this  mag- 
nificent orb  was  rightly  selected  by  Brewster  as  the 
crowning  proof  of  the  relative  insignificance  of  the 
earth  in  the  scale  of  creation — assuming  only  that  we 
can  indeed  gauge  the  purposes  of  the  Creator  by  the 
familiar  tests  of  measure  and  weight. 

Or  if  we  estimate  Jupiter  rather  by  the  forces  in- 
herent in  his  system,  if  we  contemplate  the  enormous 
rapidity  with  which  his  vast  bulk  whirls  round  upon 
its  axis,  or  trace  the  stately  motion  with  which  he 
sweeps  onward  on  his  orbit,  or  measure  the  influences 
by  which  he  sways  his  noble  family  of  satellites,  we  are 
equally  impressed  with  the  feeling  that  here  we  have 


124 


OTHER    WORLDS  THAN  OURS. 


the  prince  of  all  the  planets,  the  orb  which,  of  all  others 
in  the  solar  scheme,  suggests  to  us  conceptions  of  the 
noblest  forms  of  life. 

The  very  symmetry  and  perfection  of  the  system 
which  circles  round  Jupiter  have  led  many  to  believe 
that  he  must  be  inhabited  by  races  superior  in  intelli- 
gence to  any  which  people  our  earth.  The  motions 
of  these  bodies  afford  indeed  to  our  astronomers  a  no- 
ble subject  of  study.  Our  most  eminent  mathemati- 
cians have  given  many  hours  of  study  to  the  phenome- 
na which  the  four  moons  present  to  the  terrestrial  ob- 
server. But  we  can  trace  only  the  general  movements 
of  the  satellites  of  Jupiter.  Their  minor  disturbances, 
the  effects  of  the  varying  influences  which  the  sun  and 
Jupiter  exert  upon  them,  and  which  the  moons  exert 
upon  each  other,  must  tax  the  powers  of  far  abler 
mathematicians  even  than  he  who  "surpassed  the 
whole  human  race  in  mental  grasp." 

But,  after  all,  we  must  judge  of  Jupiter  rather  ac- 
cording to  the  evidence  we  have,  and  the  analogies 
which  are  most  directly  applicable  to  the  case,  than 
according  to  fancies  such  as  these.  We  know  that 
the  sun,  which  surpasses  Jupiter  in  weight  and  vol- 
ume even  more  than  Jupiter  surpasses  the  earth,  is 
yet  not  the  abode  of  life,  so  that  mere  size  and  mass 
must  not  be  held  to  argue  habitability.  We  know 
that  many  meteors  and  comets  sweep  through  spaces 
more  swiftly  than  the  vast  bulk  of  Jupiter,  so  that  the 
energies  indicated  by  mere  velocity  of  motion,  whether 
orbital  or  rotational,  must  be  equally  disregarded. 
Nor  must  we  forget  that,  ages  before  men  studied  the 


JUPITER,  GIANT  OF  THE  SOLAR  SYSTEM.      125 

{notions  of  our  own  moon,  she  presented  the  same 
noble  subject  of  study  that  she  forms  in  our  day  for 
an  Adams,  a  Leverrier,  or  a  Delaunay.  Even  now  a 
thousand  grand  problems  are  presented  to  our  men  of 
science  which  escape  their  notice ;  and  we  might  as 
reasonably  argue  that  there  must  be  creatures  existing 
unperceived  among  us,  who  deal  with  these  problems, 
as  that,  out  yonder  in  space,  there  must  be  beings 
who  study  the  complicated  motions  of  the  Jovial 
satellites. 

Jupiter  presents  the  following  principal  physical 
habitudes : 

He  has  a  diameter  of  about  eighty-five  thousand 
mile's,  or  nearly  eleven  times  as  large  as  the  earth's,  a 
surface  one  hundred  and  fifteen  times  larger,  and,  as  I 
have  said,  a  volume  more  than  twelve  hundred  times 
larger.  Gravity  at  his  surface  is  about  two  and  a  half 
times  as  great  as  on  our  earth's,  so  that  such  creatures 
as  exist  around  us  would  find  their  weight  much  more 
than  doubled  if  they  were  removed  to  Jupiter.  He 
lies  more  than  five  times  farther  from  the  sun  than 
our  earth,  and  the  light  and  heat  which  he  receives 
from  that  orb  are  reduced  to  about  one-twenty-fifth  of 
our  supply.  He  rotates  on  his  axis  in  rather  less  than 
ten  hours  (nine  hours,  fifty-five  minutes,  twenty-six 
seconds),  so  that  the  length  of  his  day  is  considerably 
less  than  half  of  ours.  His  axis  is  nearly  perpendicu- 
lar to  his  orbit,  so  that  there  are  no  appreciable  sea- 
sonal changes  as  he  sweeps  round  the  sun  in  his  long 
year  of  4,332£  days. 

It  will  be  convenient  to  consider,  first,  the  proba- 


126  OTHER   WORLDS  THAN  OURS. 

ble  influence  of  the  great  attractive  power  of  Jupiter 
upon  the  dimensions  of  the  various  orders  of  living 
creatures  existing  upon  his  surface. 

The  grandeur  of  his  orb  naturally  suggests,  at  first 
sight,  the  idea  of  beings  far  exceeding,  both  in  might 
and  bulk,  those  which  live  upon  the  earth.  Old 
Wolfius  was  led  to  a  similar  conclusion  in  another 
way.  I  quote  his  quaint  fancies  as  quaintly  presented 
by  Admiral  Smyth.  "  Wolfius,"  says  the  genial  sailor, 
"not  only  asserts  that  there  are  inhabitants  in  Jupiter, 
but  also  shows  that  they  must  necessarily  be  much 
larger  than  those  of  the  earth  ;  in  fact,  that  they  are 
of  the  giant  kind,  and  nearly  fourteen  feet  high  by 
tfyd-measurement.  And  thus  he  proves  it.  It  is 
shown  in  optics,  that  the  pupil  of  the  eye  dilates  and 
contracts  according  to  the  degree  of  light  it  encoun- 
ters. "Wherefore,  since  in  Jupiter  the  sun's  meridian 
height  is  much  weaker  than  on  the  earth,  the  pupil 
will  need  to  be  much  more  dilatable  in  the  Jovial 
creature  than  in  the  terrestrial  one.  But  the  pupil  is 
observed  to  have  a  constant  proportion  to  the  ball  of 
the  eye,  and  the  ball  of  the  eye  to  the  rest  of  the 
body ;  so  that,  in  animals,  the  larger  the  pupil  the 
larger  the  eye,  and  consequently  the  larger  the  body. 
Assuming  that  these  conditions  are  unquestionable, 
he  shows  that  Jupiter's  distance  from  the  sun,  com- 
pared with  the  earth's,  is  as  twenty-six  to  five ;  the 
intensity  of  the  sun's  light  in  Jupiter  is  to  its  intensity 
on  the  earth  in  a  duplicate  ratio  five  to  twenty-six." 
The  eyes  of  the  Jovials  and  their  dimensions  generally 
must  be  correspondingly  enlarged,  and  "  it  therefore 


JUPITER,  GIANT  OF  THE  SOLAR  SYSTEM.      12; 

follows  that  even  Goliath  of  Gath  would  have  cut  but 
a  sorry  figure  among  the  natives  of  Jupiter.  That  is, 
supposing  the  Philistine's  altitude  to  be  somewhere 
between  eight  feet  and  eleven,  according  as  we  lean 
to  Bishop  Cumberland's  calculation,  or  the  Vatican 
copy  of  the  Septuagint.  Now,  Wolfius  proves  the 
size  of  the  inhabitants  of  Jupiter  to  be  the  same  as 
that  of  Og,  king  of  Bashan,  whose  iron  camp-bed  was 
nine  cubits  in  length  and  four  in  breadth — or  rather 
he  shows,  in  the  way  stated,  the  ordinary  altitude  of 
the  Jovicolse  to  be  13^^-  Paris  feet,  and  the  height 
of  Og  to  have  been  13-Lfff  feet.  See  his  "Works,  vol. 
iii.,  p.  438." 

This  exact  determination  of  the  dimensions  of 
Jovial  men  would  be  very  pleasing  and  satisfactory, 
were  it  not  that  another  line  of  argument  guides  us  at 
least  as  conclusively  to  a  very  different  view.  If  we 
are  to  assume  that  beings  resembling  men  in  all  attri- 
butes except  size,  actually  exist  on  Jupiter,  we  might 
claim  for  these  beings  the  power  of  moving  from  place 
to  place  as  freely  as  we  do,  with  quite  as  much  reason 
as  Wolfius  claimed  for  them  the  same  powers  of  vis- 
ion that  we  possess.  Proceeding  according  to  this 
view,  we  are  led  to  the  conclusion  that  the  Jovicolm 
are  pygmies  about  two  and  a  half  feet,  on  the  average, 
in  height.  For  we  know  that  a  man  removed  to  Jupi- 
ter would  weigh  about  two  and  a  half  times  as  much 
as  he  does  on  our  own  earth.  He  would  thus  be  op- 
pressed with  a  burden  equivalent  to  half  as  much 
again  as  his  own  weight.  This  would  render  life  it- 
eelf  an  insupportable  burden ;  and  we  have  to  inquire 


128  OTHER   WORLDS  THAN  OURS. 

what  difference  of  size  would  suffice  to  make  a  Jove- 
man  as  active  as  our  terrestrial  men.  Now,  the  weight 
of  bodies  similarly  proportioned  varies  as  the  third 
power  of  the  height ;  for  example,  a  body  twice  as 
high  as  another — in  other  respects  similar — will  be 
eight  times  as  heavy.  But  the  muscular  power  of  ani- 
mals varies  as  the  cross-section  of  corresponding  mus- 
cles, or  obviously  as  the  square  of  the  linear  dimen- 
sions ;  so  that  of  two  animals  similarly  constituted, 
but  one  twice  as  high  as  the  other,  the  larger  would 
be  four  times  the  more  powerful.  He  would  weigh, 
however,  eight  times  as  much  as  the  other.  He  would 
therefore  be  only  half  as  active.  Similarly,  an  animal 
three  times  as  high  as  another  of  similar  build,  would 
be  only  one-third  as  active ;  and  so  on  for  all  such 
relations.  Now,  since  a  terrestrial  man  removed  to 
Jupiter  would  be  two  and  a  half  times  as  heavy  as  on 
the  earth,  it  follows  obviously  that  a  man  on  Jupiter 
proportioned  like  our  terrestrial  men  would  be  as  ac- 
tive as  they  are,  if  his  height  were  to  theirs  as  one  to 
two  and  a  half.  Hence,  setting  six  feet  as  the  maxi- 
mum ordinary  height  of  men  on  the  earth,  we  see  that 
the  tallest  and  handsomest  of  the  Jovicolse  can  be  but 
two  and  a  half  feet  in  height,  if  only  our  premises 
are  correct.  Thus,  Tom  Thumb  and  other  little  fel- 
lows, if  removed  to  Jupiter,  might  be  wondered  at  for 
their  enormous  height,  and  eagerly  sought  after  by 
any  Carlylian  Fredericks  who  may  be  forming  grena- 
dier corps  out  yonder. 

One  line  of  argument  having  thus  led  us  to  regard 
the  Jovicolae  as  Ogs  of  Bashan,  while  another  equally 


JUPITER,  GIANT   OF  THE  SOLAR  SYSTEM.      129 

plausible  lias  reduced  their  dimensions  to  those  of  our 
two-year-old  children,  we  may  fairly  conclude  that 
this  method  of  reasoning  is  fallacious.  We  must  not 
measure  the  inhabitants  of  other  worlds  according 
to  the  conceptions  suggested  by  the  forms  of  life  we 
are  acquainted  with  upon  earth.  "We  must  admit  the 
possibility  that  arrangements,  as  different  from  those 
we  are  familiar  with  as  the  constitution  of  the  insect 
is  from  that  of  man,  may  be  presented  amid  the  orbs 
which  circle  round  the  sun.  It  were  unwise,  no  doubt, 
to  give  free  scope  to  speculation  where  we  have  in 
truth  no  means  of  forming  an  opinion.  We  need  not 
imagine,  as  some  have  done,  that  "  the  inhabitants  of 
Jupiter  are  bat-winged,"  or  with  others,  "  that  they 
are  inveterate  dancers."  ISTor,  to  take  the  views  of 
more  respectable  authorities,  need  we  agree  with  Sir 
Humphry  Davy,  that  the  bodies  of  the  Jovials  are 
composed  of  "  numerous  convolutions  of  tubes  more 
analogous  to  the  trunk  of  the  elephant  than  any  thing 
else ; "  with  Whewell,  that  they  are  pulpy,  gelatinous 
creatures,  living  in  a  dismal  world  of  water  and  ice 
with  a  cindery  nucleus ;  nor  finally,  with  Brewster,  that 
the  Jovial  may  have  his  "  home  in  subterranean  cities 
warmed  by  central  fires,  or  in  crystal  caves  cooled  by 
ocean-tides,  or  may  float  with  the  Nereids  upon  the 
deep,  or  mount  upon  wings  as  eagles,  or  rise  upon  the 
pinions  of  the  dove,  that  he  may  flee  away  and  be  at 
rest."  So  soon  as  we  give  a  definite  form  to  the  con- 
ceptions that  the  imagination,  free  from  the  control  of 
exact  knowledge,  frames  respecting  the  inhabitants  of 
other  worlds,  we  touch  at  once  on  the  grotesque,  the 


130 


OTHER   WORLDS  THAN  OURS. 


hideous,  or  the  ridiculous.*  It  is  sufficient  to  recog- 
nize the  probability,  or  rather  the  certainty,  that  the 
beings  of  other  worlds  are  very  different  from  any  we 
are  acquainted  with,  without  endeavoring  to  give 
shape  and  form  to  fancies  that  have  no  foundation  in 
fact. 

"We  may  regard  it  as  probable,  however,  that  living 
creatures  in  Jupiter,  if  any  exist,  are  built  generally 
on  a  much  smaller  scale  than  those  which  people  our 
earth.  Trees,  plants,  and  the  vegetable  world  gener- 
ally, must  also,  one  would  imagine,  be  very  differently 
constituted  from  those  we  are  familiar  with.  It  is  well 
known  that  the  motion  of  the  vegetable  juices  is  in 
part  regulated  by  the  force  of  gravity,  and  therefore 
it  must  be  admtited  that  the  structure  of  terrestrial 
plants  is  in  part  dependent  upon  the  value  of  gravita- 
tion at  the  earth's  surface.  Whewell,  in  his  "  Bridg- 
water  Treatise  "  on  the  astronomical  evidence  of  design 
in  Creation,  lays  great  stress  on  this  relation,  pointing 

*  It  may  be  worth  while  to  gather  a  lespon  from  this  circumstance. 
We  know  that  every  form  of  life  is  replete  with  evidences  of  adaptation 
(no  matter  how  secured)  to  the  conditions  which  surround  it.  We  have 
thus  evidenced  to  us,  as  forcibly  as  possible,  the  perfection  of  the  laws 
by  which  the  Creator  rules  the  universe,  and  a  measure  (if  one  may  so 
speak)  even  of  that  which  is  inconceivable  by  us — His  infinite  wisdom. 
Now,  man,  with  all  his  knowledge  of  the  Creator's  ways,  yet  so  soon  as 
he  passes  the  boundary  of  the  known,  pictures  to  himself  all  manner  of 
unnatural  and  impossible  forms  of  existence.  Even  the  unknown  parts 
of  our  own  earth  have  been  peopled  ere  now,  in  imagination,  with  "men 
whose  heads  do  grow  beneath  their  shoulders,"  and  other  similarly  in- 
congruous  beings.  It  is  more  excusable,  perhaps,  that  an  anatomically 
impossible  structure  should  have  been  assigned  to  angels  (the  cherubim 
have  been  even  more  unfortunate),  while  the  Evil  One,  that  "  goeth  about 
as  a  roaring  lion,"  has  had  the  principal  attributes  of  a.  class  of  ruml 
nantia  assigned  to  him. 


JUPITER,  GIANT  OF  THE  SOLAR  SYSTEM.      131 

out,  if  I  remember  right,  that  all  vegetation  would  be 
destroyed  at  once  if  there  could  suddenly  take  place 
any  marked  change  in  the  earth's  attractive  forces. 
If  this  view  is  correct,  it  is  certain  that  none  of  our 
plants  could  thrive  on  the  soil  of  Jupiter. 

The  year  of  Jupiter  differs  in  a  much  more  striking 
manner  than  that  of  Mars  from  our  terrestrial  year. 
It  consists  of  nearly  twelve  such  years  as  ours,  so  that 
the  period  corresponding  to  one  of  our  seasons  lasts 
nearly  three  years,  and  a.Jovial  month  is  nearly  equal 
to  one  of  our  terrestrial  years.  He  has,  however,  no 
seasons  in  our  sense  of  the  word,  since  his  equator  is 
inclined  but  little  more  than  three  degrees  to  his  orbit. 
Thus  a  perpetual  spring  reigns  all  over  his  surface. 

But  before  we  proceed  to  form  a  high  opinion  of 
the  planet's  condition  under  the  influence  of  this 
perpetual  spring,  let  us  distinctly  understand  what  the 
words  mean.  The  word  spring  has  a  genial  sound  to 
ourselves,  because  we  associate  it  with  that  which  is 
commonly  the  pleasantest  portion  of  our  year ;  but  it 
is  just  possible  that  the  perpetual  spring  reigning  over 
Jupiter,  though  doubtless  well  adapted  to  the  wants 
of  his  inhabitants,  leads  to  a  state  of  things  such  as  we 
might  not  find  altogether  so  agreeable. 

Admiral  Smyth  says  that  "  as  the  rays  of  the  sun 
fall  perpendicularly  on  the  body  of  the  planet,*  and 

*  In  the  same  paragraph  Admiral  Smyth  says  that,  as  seen  from 
Jupiter's  equatorial  regions,  the  sun  would  seem  to  move  through  the 
heavens  with  great  rapidity,  while  near  the  polar  regions  the  sun's 
•jnotion  will  be  comparatively  slow,  and  he  will  be  seen  to  describe  only 
a  small  semicircle  above  the  horizon.  The  direct  reverse  is,  however, 
the  case,  the  sun's  path  and  the  rapidity  of  his  apparent  diurnal  motion 


132 


OTHER   WORLDS   THAN  OURS. 


always  continue  to  do  so,  the  heat  must  be  as  nearly 
as  possible  equal  at  all  times  of  the  year — a  perennial 
summer:  this  is  a  striking  display  of  beneficent  ar- 
rangement." But  we  must  be  cautious  in  adopting 
this  mode  of  argument  in  dealing  with  the  Creator's 
ways.  That  the  arrangement  is  beneficent,  we  need 
not  of  course  question.  But  that  we  can  recognize 
the  way  in  which  it  is  beneficent  is  quite  another  mat- 
ter. If  Jupiter's  great  distance  from  the  sun  is  com- 
pensated for  by  this  peculiar  disposition  of  his  axis, 
and  we  are  to  admire  the  beneficence  thus  displayed, 
are  we  therefore  to  find  fault  with  the  Creator  for 
not  dealing  similarly  with  Saturn,  Uranus,  and  Nep- 
tune, which,  being  farther  from  the  sun,  have  greater 
need  than  Jupiter  of  some  special  adaptation  of  the 
sort  ?  It  seems  safer  to  consider  the  consequences 
which  flow  from  the  arrangement  without  any  special 
reference  to  the  design  of  the  Creator  in  permitting 
them,  lest,  in  our  over-anxiety  to  recognize  beneficence 
in  the  treatment  of  one  world,  we  should  adopt  a 
mode  of  reasoning  which  leads  to  the  direct  conclu- 
sion that  other  worlds  have  been  ill-cared  for. 

being  nearly  constant  for  all  parts  of  Jupiter,  and  throughout  his  year. 
Admiral  Smyth  seems  to  have  thought  that  the  variations  of  the  sun's 
path  in  Jupiter  corresponded  to  those  observed  in  the  progress  of  a  year 
at  any  place  on  the  earth's  equator,  the  sun  always  rising  vertically 
and  always  describing  a  complete  semicircle,  though  attaining  different 
altitudes  at  different  seasons.  The  real  fact  is,  that  in  all  parts  of 
Jupiter  the  sun  describes  a  complete  diurnal  semicircle,  attaining  a 
different  midday  altitude  in  different  places.  But,  as  he  always  rises 
nearly  due  east,  and  sets  nearly  due  west  (as  he  docs  in  spring-time  all 
over  the  earth),  he  necessarily  crosses  the  horizon  at  different  angles  as 
seen  in  different  places,  and  always  describes  about  half  of  a  great 
circle  of  the  spheie. 


JUPITER,  GIANT  OF  THE  SOLAR  SYSTEM.      133 

The  great  peculiarity  resulting  from  the  arrange- 
ment in  question — the  only  peculiarity,  in  fact,  of 
which  we  can  speak  with  any  confidence — consists  in 
this,  that,  everywhere  on  Jupiter,  day  and  night  are  of 
equal  length.  It  is  in  this  sense  only  that  perpetual 
spring — or  perpetual  autumn,  if  we  please — reigns  on 
the  giant  planet.  The  different  latitudes  of  Jupiter 
have  climates  differing  quite  as  much  as  those  found 
in  different  latitudes  on  our  own  earth.  At  the 
equator  the  sun  passes  every  day  nearly  to  the  point 
overhead.  At  the  poles  the  sun  seems  to  glide  along 
the  horizon,  rising  in  the  east,  passing  round — always 
near  the  horizon — toward  the  south,  and  thence  to 
his  setting-place  in  the  west.  In  intermediate  lati- 
tudes, the  sun  passes  to  a  southerly  elevation  which  is 
greater  or  less,  according  as  the  place  is  nearer  to  or 
farther  from  Jupiter's  equator.  It  follows  that  there 
is  a  marked  difference  between  the  sub-equatorial  and 
the  sub-polar  regions  in  Jupiter,  while  between  these 
regions  every  intermediate  climate  is  to  be  found. 

Owing  to  the  rapidity  of  Jupiter's  rotation,  the 
motion  of  the  sun  in  the  Jovial  sky  must  be  much 
more  readily  discernible  and  measurable  than  that 
with  which  the  sun  seems  to  pass  across  our  own 
heavens.  He  traverses  the  whole  semicircle,  from  the 
eastern  to  the  western  horizon,  in  two  minutes  less  than 
five  hours,  or  about  six  degrees  in  ten  minutes.  This 
corresponds  to  a  motion  through  a  space  equal  to  the 
Bun's  diameter  (as  we  see  him)  in  fifty  seconds,  and 
must  be  readily  discernible,  even  to  the  unaided  vision 
of  the  Jovicolse,  unless  their  eyesight  is  much  infe- 


134  OTHER    WORLDS  THAN  OURS. 

rior  to  ours.  The  smallness  of  the  sun,  as  seen  from 
Jupiter,  must  help  to  render  the  motion  more  percep- 
tible. He  presents  to  them  an  apparent  diameter  only 
equal  to  about  one-fifth  of  that  with  which  we  see 
him,  so  that  in  ten  seconds  he  seems  to  pass  over  a 
space  equal  to  his  own  diameter. 

The  other  celestial  bodies  are  affected  with  similar 
motions  as  seen  from  Jupiter.  Of  course,  those  seen 
near  the  poles  of  his  heavens  seem  relatively  at  rest. 
One  of  these  poles  lies  in  the  heart  of  the  constellation 
Draco ;  the  other  lies  close  by  the  great  Magellan ic 
Cloud,  which  must  present  a  magnificent  cynosure  to 
the  inhabitants  of  the  southern  hemisphere  of  the 
planet.  The  contrast  between  the  steadfastness  of 
the  polar  star-groups  and  the  swift  motions  of  the 
equatorial  constellations,  must  be  impressive  indeed. 
These  equatorial  groups  are  no  other  than  our  old 
friends  the  zodiacal  constellations.  As  seen  by  the 
inhabitants  of  Jupiter,  they  rise  with  a  perceptible 
but  stately  motion  above  the  eastern  horizon,  pass  to 
their  culmination  on  the  southern  meridian,  and  so  to 
their  setting-place  in  the  west — exhibiting  the  same 
splendors  which  the  terrestrial  astronomer  delights  to 
gaze  upon,  enhanced  by  the  peculiar  impressions  of 
active  power  suggested  by  visible  and  obvious  motion. 

It  may  seem,  at  first  sight,  that  the  presence  of  the 
Jovial  satellites  must  tend  to  dim  the  splendor  of  the 
sidereal  heavens.  Our  own  moon,  despite  the  beauti- 
ful passage  *  in  which  Homer  has  described  the  calm 

*  Homer  must  not  be  held  responsible  for  Pope's  amazing  description, 
which,  strangely  enough,  has  found  an  ardent  admirer  in  one  of  our 


JUPITER,  GIANT  OF  THE  SOLAR  SYSTEM.      135 

beauty  of  a  moonlit  night,  certainly  detracts  largely 
from  the  magnificence  of  the  star-groups ;  and  as  at 
times  there  must  be  four  moons  visible  above  the 
horizon  of  the  Jovials,  it  might  seem  that  all  but  the 
brighter  stars  would  be  quite  obliterated.  The  first 
moon  must  appear  somewhat  larger  than  our  own; 
the  next  has  an  apparent  diameter  rather  more  than 
half  as  large  as  that  of  our  moon ;  the  third  (really 
the  largest)  appears  about  as  large  as  the  second ;  and 
the  fourth  has  an  apparent  diameter  equal  to  about  a 
quarter  of  our  moon's.  Thus,  in  all,  they  cover  a 
space  on  the  sky  more  than  half  as  large  again  as  that 
which  our  moon  covers.  But,  in  reality,  they  cannot 
have  nearly  so  marked  an  effect  in  dimming  the  lus- 
tre of  the  stars.  For  it  must  not  be  forgotten  that 
they  shine  only  by  reflecting  the  sun's  light,  and  that 
he  illuminates  them  but  faintly,  in  comparison  with 
the  light  he  pours  upon  our  own  moon.  In  effect, 
supposing  their  reflective  capacities  equal  to  the 
moon's,  they  must  appear  less  brilliant  than  she  does, 
in  the  proportion  of  about  one  to  twenty-five;  and 
combining  this  result  with  the  above  relation,  it  fol- 
lows that,  even  if  they  could  all  be  "full"  together, 
they  could  send  to  the  Jovials  but  about  one-sixteenth 
part  of  the  light  we  receive  from  the  full  moon.  But, 
as  a  matter  of  fact,  they  cannot  all  be  full  together. 
The  motions  of  the  inner  three  are  so  related,  that, 
though  there  is  nothing  to  prevent  them  from  being 

best  modern  observers.  Homer  did,  however,  mention  as  a  character. 
Lstic  of  the  moonlit  sky,  that  "  all  the  stars  shine,"  a  proof  that  some 
times,  as  Horace  tells  us,  the  great  master  nodded. 


136  OTHER   WORLDS  THAN  OURS. 

all  visible  together,*  yet  when  so  visible,  one  only  can 
be  full.  The  fourth  may  be  full  at  the  same  time,  or, 
in  fact,  may  be  combined  with  the  other  three  ia  any 
way,  since  its  motions  are  not  bound  up  with  theirs  as 
theirs  are  inter  se. 

Even  now,  however,  we  have  not  reached  a  full 
estimate  of  the  extent  of  the  mistake  which  those  as- 
tronomers have  made  who  speak  of  the  splendor  with 
which  the  satellites  of  Jupiter  illuminate  his  skies. 
When  at  that  part  of  their  orbits  where  they  would 
otherwise  be  full,  the  three  inner  moons  are  always 
eclipsed,  and  though  the  fourth,  by  reason  of  its  great 
distance,f  sometimes  escapes  eclipse,  yet  more  fre- 
quently it  is  obscured  like  the  others.  The  two  inner 
satellites  are  eclipsed  for  upward  of  two  hours,  and  as 
they  occupy  but  a  few  hours  in  completing  their  cir- 
cuit round  the  sky,  $  it  will  be  seen  how  largely  this 
relation  detracts  from  their  light-supplying  powers. 

We  see,  then,  that  those  writers  have  been  mis- 
taken who  allege  that  the  great  distance  of  Jupiter 
from  the  sun  is  compensated  by  the  number  of  his 
moons,  and  the  quantity  of  light  they  reflect  toward 
him.  So  far  is  this  from  being  the  case,  that,  under 
the  most  favorable  circumstances,  they  can  supply 

*  Or  all  invisible  together.  Lardner  asserts  the  contrary ;  so  that 
one  would  imagine  he  had  never  seen  all  the  moons  together  on  the 
same  side  of  Jupiter. 

f  Not  on  account  of  the  inclination  of  its  orbit  being  large,  as  Sir 
John  Herschel  has  said.  The  orbit  of  this  satellite  is,  indeed,  less  in- 
clined  than  the  orbits  of  the  others. 

\  Moving  in  a  direction  contrary  to  that  due  to  the  rotation  of 
Jupiter,  they  of  course  remain  longer  above  the  horizon  than  the  sun 
or  the  equatorial  fixed  stars. 


JUPITER,  GIANT  OF  THE  SOLAR  SYSTEM.      137 

during  the  Jovial  night  but  about  one-twentieth  part 
of  the  light  with  which  the  full  moon  illuminates  our 
nocturnal  skies.  The  poetical  descriptions  which  im- 
aginative writers  have  indulged  in,  respecting  the 
splendor  of  the  scene  presented  by  these  satellites, 
will  not  bear  the  dry  light  of  numerical  estimation. 
That  the  satellite-system  of  Jupiter  subserves  impor- 
tant functions,  and  affords,  in  reality,  like  all  the 
works  of  the  Creator,  the  amplest  evidence  of  design, 
need  not  be  questioned ;  but  that  we  have  been  able 
to  understand  the  special  purpose  for  which  they  have 
been  created — in  fine,  "  to  see,"  as  the  Creator  does, 
"  that  they  are  good  " — may  be  assuredly  denied. 

Perhaps,  if  one  were  able  to  discuss  with  advan- 
tage the  special  purposes  which  this  or  that  portion 
of  creation  is  intended  to  subserve,  it  might  be  argued 
that  the  outer  planets  have  greater  need  of  moons 
than  the  inner,  because,  their  year  being  longer,  there 
is  greater  occasion  for  objects  whose  motions  shall 
serve  as  measures  of  time.  The  satellites  of  Jupiter 
supply,  by  their  separate  motions,  convenient  meas- 
ures of  the  shorter  time-intervals  ;  while,  by  their  suc- 
cessive conjunctions,  (i.)  in  pairs,  (ii.)  the  three  inner 
together,  and  (iii.)  the  outer  with  pairs  of  the  inner, 
they  afford  convenient  measures  of  longer  intervals. 

But  let  us  turn  from  vague  guesses  at  the  purposes 
of  the  Almighty,  to  the  consideration  of  those  facts 
which  are  actually  presented  to  our  notice. 

Eecognizing  the  existence  of  varied  climatic  rela- 
tions in  different  parts  of  Jupiter,  we  have  now  to 
consider  the  climate  of  the  planet  generally,  to  con- 


I38  OTHER   WORLDS  THAN  OURS. 

template  the  position  of  this  great  orb  in  the  solar 
system,  and  to  determine  how  far  its  great  distance 
from  the  sun  may  be  compensated  by  other  relations. 

There  can  be  no  doubt  that  the  amount  of  heat 
poured  by  the  sun  on  any  portion  of  Jupiter's  surface, 
placed  perpendicularly  with  respect  to  the  heat-rays, 
must  be  very  much  less  than  the  amount  received  by 
an  equal  portion  of  our  earth's  surface,  similarly  situ- 
ated. The  direct  heating  effects  of  the  sun  must,  in 
fact,  as  already  stated,  be  less  on  Jupiter  than  on  our 
own  earth,  in  the  proportion  of  about  one  to  twenty- 
five.  And  it  cannot  be  doubted  that  the  effects  of 
this  difference  must  be  highly  important,  whatever 
arrangements  may  exist  to  compensate  for  the  defi- 
ciency of  heat.  If  we  can  demonstrate  in  any  way 
that  the  mean  temperature  of  the  Jovial  atmosphere 
is  equal  to  that  of  our  own  air,  or  even  greater,  yet 
the  difference  of  the  sun's  direct  heat  involves  a  variety 
of  consequences  which  we  cannot  disregard. 

We  know,  for  instance,  that  it  is  principally  the 
direct  heat  of  the  sun  that  causes  the  evaporation  of 
water  from  the  surface  of  oceans,  seas,  lakes,  and  riv- 
ers, and  therefore  all  the  important  consequences 
which  flow  from  the  presence  of  aqueous  vapor  in  large 
quantities  in  the  earth's  atmosphere.  "We  can  con- 
ceive the  existence  of  vapors  in  the  air  which  might 
keep  away  from  the  earth's  surface  the  greater  portion 
of  the  sun's  heat,  and  yet,  by  preventing  the  escape 
of  the  remainder  by  radiation  into  space,  might  leave 
the  general  warmth  of  the  air  around  us  as  great  as  it 
is  at  present.  But  it  cannot  be  doubted  that  such  an 


JUPITER,  GIANT  OF  THE  SOLAR  SYSTEM.      139 

arrangement  would  injuriously  affect  the  whole  econ- 
omy of  evaporation  and  its  consequences,  winds,  rains, 
clouds,  mist,  with  their  consequences,  so  important  for 
the  welfare  of  terrestrial  races. 

And  in  like  manner  other  effects  accruing  from  the 
direct  action  of  the  solar  rays  might  be  considered. 

It  follows,  then,  that  it  is  by  no  means  sufficient  to 
show  how  the  heat  which  falls  upon  Jupiter  may  be 
stored  up,  through  the  action  of  some  component  of 
his  atmosphere  in  preventing  its  radiation  into  space. 
It  is,  indeed,  of  the  utmost  importance  to  know  that 
even  this  is  possible,  because  we  are  thus  enabled  to 
see  that  Jupiter  is  not  necessarily  an  abode  so  bleak 
and  desolate  as  some  writers  have  imagined.  In  the 
following  passage,  Prof.  Tyndall  has  exhibited  the 
means  by  which  this  result  may  be  brought  about, 
and  the  inhabitants  of  the  noblest  planet  in  the  solar 
system  placed  somewhat  higher  in  the  scale  of  crea- 
tion than  Whewell  surmised.  "  In  these  calculations," 
he  remarked,  referring  to  Whewell's  estimate  of  the 
sun's  heating  power  on  Jupiter  and  the  other  exterior 
planets,  "  the  influence  of  an  atmospheric  envelope  was 
overlooked,  and  this  omission  vitiated  the  entire  argu- 
ment. It  is  perfectly  possible  to  find  an  atmosphere 
which  would  act  the  part  of  a  barb  to  the  solar  rays, 
permitting  their  entrance  toward  the  planet,  but  pre- 
venting their  withdrawal.  For  example,  a  layer  of 
air,  two  inches  in  thickness,  and  saturated  with  the 
vapor  of  sulphuric  ether,  would  offer  very  little  re- 
Bistance  to  the  passage  of  the  ether  rays,  but  I  find 
that  it  would  cut  off  fully  thirty-five  per  cent,  of  the 


1 4o 


OTHER    WORLDS  THAN  OURS. 


planetary  radiation.  It  would  require  no  inordinate 
thickening  of  the  layer  of  vapor  to  double  this  ab- 
sorption ;  and  it  is  perfectly  evident  that,  with  a  pro- 
tecting envelope  of  this  kind,  permitting  the  heat  to 
enter  but  preventing  its  escape,  a  comfortable  tem- 
perature might  be  obtained  on  the  surface  of  our 
most  distant  planet."  The  difference  between  such 
an  arrangement  as  this  and  the  way  in  which  the 
earth's  temperature  is  obtained,  is  the  exact  converse 
of  that  dealt  with  when  we  were  considering  the  case 
of  Mercury  and  Yenus.  Precisely  as  the  mean  tem- 
perature of  the  atmosphere  of  either  of  the  interior 
planets  may  be  no  higher  than  that  of  our  own  air, 
while  yet  the  sun's  direct  rays  continue  wholly  un- 
bearable, so  the  outer  planets  may  have  a  perfectly 
comfortable  temperature,  while  yet  that  direct  solar 
heat  which  exerts  so  many  important  influences  on  the 
earth  must  be  supplied  only  in  quantities  which  we 
should  find  wholly  inadequate  for  our  wants. 

I  am  far  from  desiring  to  infer  that  Jupiter  must 
therefore  be  uninhabited,  or  even  that  the  creatures 
existing  on  his  surface  must  necessarily  differ  wholly 
in  their  nature  from  any  with  which  we  are  familiar. 
But  I  think  that,  while,  on  the  one  hand,  we  must 
reject  one  of  the  chief  arguments  by  which  Whewell 
was  led  to  people  Jupiter  with  cartilaginous  and  gluti- 
nous creatures  (!)  floating  in  boundless  oceans,  so,  on 
the  other,  we  cannot  accept  without  question  the  ar- 
gument by  which  an  effort  has  been  made  to  indicate 
the  possibility  of  a  close  correspondence  between  Jupi- 
ter's climate  and  our  earth's. 


JUPITER,  GIANT  OF  THE  SOLAR  SYSTEM.     141 

And  here  we  are  led  to  the  most  interesting  and 
suggestive  of  all  the  relations  exhibited  by  Jupiter,  or 
rather  to  three  closely-associated  relations,  which  lead 
to  views  of  a  somewhat  startling  character. 

In  common  with  the  other  large  planets  lying  out- 
side the  zone  of  the  asteroids,  Jupiter  has  a  mean 
density  falling  very  far  short  of  the  mean  density  of 
the  earth  or  the  other  small  planets  which  travel  with- 
in that  zone.  According  to  the  best  estimates  of  his 
mass  and  apparent  diameter,  his  mean  density  would 
seem  to  be  rather  less  than  one-fourth  of  the  earth's, 
or  greater  than  the  density  of  water  by  about  one- 
third.  It  is  worthy  of  remark,  in  fact,  that  his  den- 
sity is  almost  exactly  the  same  as  the  sun's,  and  con- 
siderably greater  than  that  of  the  other  three  outer 
planets  hitherto  discovered. 

If  we  were  quite  certain  that  the  disk  measured  by 
us  exhibits  the  real  outline  of  the  planet,  or  that  his 
atmosphere  was  not  of  abnormal  extent,  and  that  his 
globe  was  solid  throughout,  it  would  follow  that  the 
substances  composing  Jupiter  were  either  altogether 
different  from  those  forming  our  earth,  or  that  they 
were  combined  in  very  different  proportions.  On  the 
last  point  we  can  form  no  opinion.  On  the  first  we 
must  be  guided  by  the  appearance  of  the  planet. 

Thus  we  are  led  to  the  second  ot  the  three  rela- 
tions just  mentioned — the  appearance  of  well-marked 
but  variable  belts  on  the  planet — and  of  other  indica- 
tions implying  the  existence  of  an  atmosphere  of  great 
extent. 

The  belts  of  Jupiter  are  commonly  arranged  with 


142  OTHER    WORLDS  THAN  OURS. 

a  certain  symmetry  on  either  side  of  the  great  equa- 
torial bright  belt,  but  sometimes  there  is  a  rather 
marked  contrast  between  the  northern  and  the  south- 
ern halves  of  the  planet.  In  color  the  dark  belts  are 
usually — when  seen  with  suitable  telescopic  power  * — 
of  a  coppery,  ruddy,  or  even  purplish  tint,  while  the 
intermediate  light  bands  \ary  from  a  pearly  white  in 
the  equatorial  belt,  through  yellowish  white  in  the 
middle  latitudes  of  both  hemispheres,  to  a  grayish  or 
even  bluish  tint  at  the  poles.  The  picture  of  Jupiter 
which  forms  the  frontispiece,  while  exhibiting  many 
of  the  features  usually  seen,  is  intended  specially  to 
illustrate  relations  presently  to  be  dealt  with. 

There  is  every  reason  to  believe  that  these  belts 
indicate  the  existence  of  a  very  extensive  vapor-laden 
atmosphere.  The  dark  belts  must  not  be  considered 
as  the  true  cloud-belts,  because  it  must  be  remembered 
that  we  look  upon  the  reverse  side  of  the  skyscape 
presented  during  the  day  to  the  Jovials :  so  that 
where  they  see  densely-compacted  dark  clouds,  we  see 
the  light  which  those  clouds  have  intercepted ;  and,  on 
the  other  hand,  where  they  see  clear  spaces,  the  light 
which  reaches  them  is  not  reflected  to  us  without  a 
considerable  loss  of  brilliancv.  Thus  the  dark  belts 


*  What  is  required  is  not  so  much  a  high  light-gathering  as  a  high 
magnifying  power,  though  both  points  are  of  importance.  When  the 
light  is  not  adequately  reduced  by  increase  of  magnifying  power,  the 
color  is  lost  hi  the  resulting  "  glare."  Reflectors  seem  to  have  an  ad- 
vantage  over  refractors  in  exhibiting  the  colors  of  the  planets  ;  at  least, 
nearly  all  the  accounts  in  which  the  appearance  of  color  has  been  spe- 
cially dwelt  upon,  have  been  received  from  observers  who  have  used 
reflectors. 


JUPITER,  GIANT  OF  THE  SOLAR  SYSTEM.      14.3 

of  Jupiter  are  those  regions  where — if  at  all — we  see 
the  true  surface  of  the  planet. 

£Tow,  viewing  the  belts  in  this  light,  have  we  any 
means  of  judging  from  their  aspect  what  is  the  extent 
of  the  planet's  atmosphere?  So  far  as  I  know,  the 
question  has  never  been  considered,  bnt  it  is  well 
worthy  of  careful  study. 

It  seems  clear,  in  the  first  place,  that  if  the  bright 
belts  really  are  cloud-belts,  and  the  dark  belts  the  sur- 
face of  the  planet,  then  on  the  edge  of  the  planet's 
disk  we  ought  to  see  some  irregularity  of  level — the 
cloud-belts  projecting  slightly  beyond  the  real  out- 
line of  the  planet — if  the  atmosphere  have  that  enor- 
mous extent  which  some  astronomers  have  supposed. 
Whether  such  an  appearance  has  ever  been  looked  for 
I  do  not  know,  but  it  has  certainly  never  yet  been 
detected. 

We  are  forced  to  conclude,  then,  that  either  the 
atmosphere  of  Jupiter  is  not  sufficiently  extensive  to 
interfere  appreciably  with  our  measurement  of  the 
planet's  bulk,  or  else  the  dark  belts  belong  but  to  a 
lower  cloud-layer,  not  to  the  planet's  real  surface. 

We  have  further  evidence  on  this  point  in  the  ap- 
pearance of  dark  spots  on  the  dusky  belts.  These 
spots  have  even  been  described  as  black,  though  surely 
their  appearing  of  that  hue  must  be  ascribed  to  the 
effect  of  contrast.  Now,  these  dark  spots,  which  have 
been  seen  by  Cassini,  Madler,  Schwabe,  Airy,  and 
others,  may  be  regarded  as  the  real  surface  of  the 
planet  (unless  they  belong  to  a  yet  deeper  cloud-layer), 
Been  for  a  while  through  openings  in  the  cloud-bed  to 


!44  OTHER    WORLDS  THAN  OURS. 

which  the  dusky  belts  belong.  The  reader  will  not 
fail  to  notice  here  some  resemblance  to  what  has  been 
already  mentioned  respecting  the  sun-spots  ;  and  when 
we  come  to  the  third  and  most  striking  of  the  associ- 
ated features  I  am  now  dealing  with,  it  will  be  seen 
that  there  may  be  more  in  the  analogy  than  one  might 
at  first  sight  be  disposed  to  imagine. 

How  far  the  appearance  of  small  round  white  spots 
on  the  dark  belts  may  be  considered  as  indicative  of 
the  extent  and  constitution  of  the  Jovial  atmosphere, 
it  is  not  very  easy  to  determine.  That  they  are  dense 
clouds,  hanging  suspended  above  the  dusky  cloud- 
layer,  must  be  admitted  as  highly  probable,  but  it  is 
open  to  question  whether  they  have  formed  there  in 
the  same  way  that  cirrus-clouds  are  seen  to  form  at  a 
great  elevation  above  a  layer  of  cumulus  clouds,  or 
whether  they  indicate  the  action  of  volcanoes  beneath 
the  dusky  layer,  propelling  enormous  streams  of  vapor 
through  the  superincumbent  cloud-beds. 

The  third  point  on  which  I  have  to  dwell  is  the 
variability  of  the  belt-system,  under  which  head  I  in- 
clude not  only  variations  in  shape  and  extent,  but 
those  much  more  significant  changes  of  color  which 
have  been  recently  discovered. 

So  far  as  is  yet  known,  there  is  no  recognizable 
law  in  the  changes  of  shape  exhibited  by  the  belts  of 
Jupiter — no  periodicity  or  intelligible  sequence.  It 
may  be  suggested,  in  passing,  that  a  systematic  and 
persistent  scrutiny  of  the  planet  might  lead  to  the  dis- 
covery of  laws  of  this  sort,  which  could  not  fail  to  in- 
dicate physical  conclusions  of  the  utmost  importance. 


JUPITER,  GIANT  OF  THE  SOLAR  SYSTEM.      145 

Nay,  further,  since  we  cannot  doubt  that  the  condition 
of  the  real  surface  of  Jupiter  is  in  some  sort  reflected, 
so  to  speak,  in  the  aspect  of  his  cloud-envelopes,  it 
seems  far  from  unlikely  that  a  scrutiny  of  this  sort 
might  tell  us  where  his  oceans  and  continents,  where 
his  deserts,  lakes,  or  rivers,  are  situated,  even  though 
no  direct  evidence  of  their  existence  might  ever  reward 
the  observer.  In  these  days,  however,  nine-tenths  of 
those  who  are  fortunate  enough  to  possess  fine  tele- 
scopes prefer  either  to  leave  them  idle,  or  to  employ 
their  powers  in  making  observations,  at  great  pains 
and  labor,  which  are  not  worth  the  paper  on  which 
they  are  recorded.*  The  few  original  observers  we 
have  are  overtasked  by  the  multitude  of  questions  of 
interest  presented  to  their  consideration,  so  that  many 
subjects  of  inquiry  must  perforce  wait,  either  till  their 
turn  arrives,  or  till  those  who  have  the  means  of 

*  It  is  painful  to  those  who  know  what  might  be  done  in  the  numer- 
ous fine  observatories  now  existing  throughout  England,  to  see  the 
powers  of  many  noble  instruments — the  chef-d'ceuvres  of  English  and 
Continental  opticians — devoted  to  puny  imitations  of  the  work  done  at 
Greenwich  and  other  similar  establishments.  I  speak  on  the  authority 
of  one  of  the  first,  if  not  the  very  first,  of  our  professional  astronomers, 
when  I  say  that  these  imitations,  even  though  they  approached  in  char- 
acter— which  they  do  not  and  cannot — the  operations  superintended  so 
ably  by  the  Astronomer  Koyal,  would  be  a  simple  waste  of  time  and 
labor.  Nor  is  this  the  only  way  in  which  fine  telescopes  are  wasted. 
While  on  every  side  there  are  subjects  of  research  which  most  pressingly 
require  investigation,  many  of  those  who  possess  the  requisite  means 
and  leisure  for  the  purpose — nay,  are  not  wanting  in  the  necessary  taste 
for  observational  research — are  unhappily  applying  themselves  to  going 
over,  perhaps  with  relatively  inferior  powers,  ground  which  has  already 
been  thoroughly  ransacked  by  our  great  observers.  With  some  ten  or 
twelve  exceptions — which  it  is  unnecessary  to  name — our  private  ob- 
servatories seem  to  have  banished  every  thing  resembling  originality. 
7 


146 


OTHER    WORLDS  THAN  OURS. 


studying  them  choose  to  turn  their  thoughts  from  the 
sterile  subjects  they  are  now  engaged  upon. 

So  far,  then,  as  inquiries  have  as  yet  been  pushed, 
all  that  can  be  asserted  on  the  subject  we  are  consid- 
ering is,  that  the  planet's  belts  vary  greatly  in  form, 
extent,  and  general  appearance.  At  one  time  the 
dusky  belts  cover  a  large  proportion  of  the  planet's 
disk,  at  another  they  are  singularly  narrow.  Now 
they  are  very  regularly  disposed,  now  they  seem  in 
Borne  way  under  the  action  of  disturbing  forces  of 
great  intensity,  causing  them  to  assume  the  most  ir- 


Fio.  1. — The  Planet  Jupiter  (Browning). 

regular  figure.    The  accompanying  picture  of  the  plan- 
et (Fig.  1)  as  seen  by  Mr.  Browning,  with  one  of  his 


JUPITER,  GIANT  OF  THE  SOLAR  SYSTEM,     i^j 

own  reflectors,  indicates  an  appearance  not  uncom- 
monly seen,  a  dark  streak  extending  obliquely  across 
the  planet's  equatorial  regions.  The  number  of  belts 
is  singularly  variable.  Sometimes  only  one  has  been 
Been,  at  others  there  have  been  as  many  as  five  or  six 
on  each  side  of  the  planet's  equator.  In  the  course  of 
a  single  hour,  Cassini  saw  a  complete  new  belt  form 
on  the  planet,  and  on  December  13,  1690,  two  well- 
marked  belts  vanished  completely,  while  a  third  had 
almost  disappeared  in  the  same  short  interval  of  time. 
But  if  we  seem  to  recognize  here  the  action  of 
forces  much  more  intense  than  those  which  influence 
the  condition  of  the  earth's  atmosphere,  we  have  still 
more  striking  evidence  to  the  same  purpose  in  the 
changes  of  color  which  have  recently  been  detected  in 
the  great  equatorial  belt.  This  belt  is  usually  of  a  pearly 
white  tint,  and  has  long  been  recognized  as  one  of  the 
most  constant  features  of  the  planet's  aspect.  As  the 
mean  surface  of  this  belt  cannot  be  less  than  a  fifth  of 
the  whole  surface  of  the  planet,  it  is  clear  that  any 
changes  which  may  take  place  in  its  general  aspect  can- 
not but  be  of  the  utmost  significance.  !N"ow,  during  the 
autumn  of  1869  and  the  spring  of  1870,  this  belt  has 
been  more  strongly  colored  than  any  part  of  the 
planet.  Mr.  Browning  (to  whom  I  am  indebted  for  the 
beautiful  painting  of  Jupiter,  which  formed  the  design 
from  which  the  frontispiece  has  been  taken),  observing 
Jupiter  in  the  earlier  part  of  the  above-named  interval, 
found  the  equatorial  belt  of  a  greenish-yellow  color, 
which  deepened  in  October,  1869,  to  a  full  ochreish 
yellow,  and  in  January  of  the  present  year  had  assumed 


148  OTHER    WORLDS  THAN  OURS. 

an  even  darker  tint,  resembling  yellow  ochre.  On  one 
occasion,  and  on  one  only,  lie  detected  this  tint  in  the 
first  bright  belt  north  of  the  equator.  While  thus  ex- 
hibiting strongly-marked  and  changing  colors,  the 
equatorial  belt  has  lost  its  right  to  be  called,  par  ex- 
cellence, the  bright  belt  of  the  planet,  being  consider- 
ably inferior  in  brilliancy  to  the  narrow  bright  belts 
north  and  south  of  it. 

Other  observers  have  also  seen  these  colors.  Mr. 
Slack,  with  a  6-inch  Browning- With  reflector,  and 
Mr.  Brindley,  with  an  8^-inch  telescope  of  the  same 
construction,  have  witnessed  most  of  the  changes  of 
color  above  described ;  and  I  myself,  using  Mr. 
Browning's  12^-inch  telescope,  found  the  greenish- 
yellow  tint  of  the  equatorial  belt  last  autumn  altogether 
unmistakable.* 

In  the  phenomena  here  described  we  have  a  prob- 
lem whose  interpretation  is  far  from  easy.  Changes  in 
the  shape,  disposition,  and  extent  of  the  dark  belts  are 
sufficiently  intelligible  when  we  associate  them,  as  we 
seem  justified  in  doing,  with  variations  in  the  position 
of  the  currents  which  traverse  the  vaporous  envelope 
of  Jupiter  as  the  trades  and  counter-trades  traverse 
the  earth's  atmosphere.  But  the  equatorial  zone  is 
Jupiter's  belt  of  calms,  resembling  in  this  respect  the 
equatorial  region,  called  by  sailors  the  "  doldrums," 

*I  had  written  thus  far  only,  when  I  attended  the  meeting  of  the 
Royal  Astronomical  Society  on  January  14, 1870,  where  Mr.  Buckingham, 
the  owner  of  the  great  refractor,  2l£  inches  in  aperture,  from  whose  pei-- 
formance  so  much  was  expected,  mentioned  that,  as  seen  with  this 
powerful  instrument,  the  great  belt  was  resolved  into  a  number  of  small 
eolored  clouds  on  a  white  ground. 


JUPITER,  GIANT   OF  THE  SOLAR  SYSTEM.     149 

and,  though  occasional  storms  might  be  expected  to 
agitate  this  region,  yet  processes  of  change,  continuing 
for  several  months  in  succession,  can  evidently  not  be 
attributed  to  any  such  cause.  We  are  taught,  by  the 
progress  of  recent  research,  to  regard  the  color  of 
the  light  derived  from  any  source  as  a  relation  of  the 
most  instructive  character,  and  changes  of  color, 
especially  changes  affecting  so  enormous  a  body  as 
Jupiter,  and  so  extensive  a  proportion  of  his  surface, 
cannot  but  be  looked  upon  as  highly  significant.  Sup- 
posing we  regard  the  ordinarily  white  light  of  the 
equatorial  belt  as  indicative  of  the  existence  of 
enormous  masses  of  cloud  reflecting  ordinary  solar 
light  to  us,  then  we  should  have  to  regard  the  appear- 
ance of  any  other  color  over  this  region  as  an  indica- 
tion that  these  cloud-masses  had  been,  through  some 
unknown  cause,  either  wholly  or  in  part  swept  away. 
But — passing  over  the  objection  that  this  view  leaves 
our  difficulty  unexplained — even  if  we  assumed  that  in 
this  way  a  portion  of  the  surface  of  Jupiter  had  been 
brought  into  view,  wholly  or  partially,  why  should  this 
surface  not  exhibit  a  constant  appearance  ?  We  cannot 
suppose  changes  affecting  Jupiter's  real  surface  are 
taking  place  with  sufficient  rapidity  to  explain  the 
series  of  strange  color-changes  observed  by  Messrs. 
Browning,  Slack,  and  other  astronomers.  But  if,  on  the 
other  hand,  we  assume  that  a  portion  of  the  light  ordi- 
narily received  from  the  bright  belt  is  inherent — that 
is,  that  the  planet  is,  to  some  extent,  self-luminous — • 
then  there  remains  the  difficulty  of  explaining  by  what 
conceivable  processes  the  equatorial  regions  are  filled 


150 


OTHER    WORLDS  THAN  OUR&. 


with  a  yellow  light,  so  full  and  bright  as  to  reach  our 
earth  from  beyond  four  hundred  millions  of  miles. 

But  I  have  spoken  of  the  three  relations  last  con- 
sidered— the  small  density  of  Jupiter,  his  extensive  at- 
mosphere, and  the  changes  which  take  place  in  the 
shape  and  color  of  his  belts — as  associated  phenomena. 
It  remains  that  I  should  endeavor  to  justify  this  state- 
ment. 

We  know  that  Whewell,  reasoning  from  the  low 
specific  gravity  of  Jupiter,  was  led  to  the  conclusion 
that  either  the  substance  of  the  planet  is  wholly  watery, 
or  else  a  few  cinders  in  the  centre  of  Jupiter's  globe 
constitute  the  only  sclid  portion  of  his  substance.  It 
need  hardly  be  said  that  the  whole  progress  of  modern 
astronomy  is  opposed  to  this  view.  We  have  seen 
that  in  the  sun  the  same  elements  exist  as  in  the  earth, 
and  that  in  the  only  planet  whose  nature  we  have  been 
able  to  examine  satisfactorily  we  find  evidence  of  the 
existence  of  the  same  forms  of  matter  that  we  see 
around  us.  It  cannot  but  be  held  as  highly  improb- 
able that  the  earth  is  the  only  member  of  the  planetary 
system  whose  substance  thus  closely  resembles  that  of 
the  parent  orb,  nor  is  it  likely  that  Mars  is  the  only 
planet  whose  general  atmospheric  constitution  resem- 
bles the  earth's.  Far  more  probably  the  lesson  we 
are  really  to  learn  from  these  circumstances  is,  that 
throughout  the  solar  system  a  general  similarity  of 
constitution  exists,  the  sun  being,  so  to  speak,  the 
type  of  the  family  over  which  he  rules.  Differences 
of  condition  we  are  compelled  to  recognize,  since  the 
sun  itself,  though  constituted  of  the  same  elements  as 


JUPITER,  GIANT  OF  THE  SOLAR  SYSTEM.      1?1 

the  earth,  is  in  so  different  a  state  and  has  a  mean 
density  relatively  so  small;  but  we  have  no  evidence 
justifying  us  in  believing  that  any  important  differ- 
ences of  constitution  exist  throughout  the  solar  system. 
Thus,  we  are  led  to  regard  the  singularly  small 
density  of  Jupiter  and  of  the  other  planets  outside  the 
orbits  of  the  asteroids,  as  due  rather  to  some  peculiarity 
in  the  condition  of  these  orbs  than  to  any  such  pecu- 
liarity of  structure  as  "Whewell  insisted  on.  It  will 
be  seen  at  once  that  Jupiter's  extensive  atmospheric 
envelope  and  the  strange  changes  in  the  aspect  of  his 
belts  are  circumstances  which  tend  strikingly  to  confirm 
this  impression.  Let  it  be  remembered  that,  supposing 
Jupiter's  globe  even  to  be  wholly  covered  with  water, 
yet  a  sun  twenty-five  times  farther  off  than  ours  could 
not  by  any  possibility  load  his  atmosphere  with  the 
enormous  masses  of  vapor  actually  present  in  it.  Let 
it  be  remembered,  further,  that  the  relatively  slug- 
gish action  of  the  sun  upon  Jupiter  could  not  by  any 
possibility  give  rise  to  atmospheric  disturbances  so  tre- 
mendous as  those  which  are  evidenced  by  the  rapid 
changes  of  figure  of  his  cloud-bands.*  Wlien  to  this 

*  It  is  worthy  of  consideration,  also,  that  even  though  the  sun  acted 
as  efficiently  upon  the  air  and  oceans  of  Jupiter  (assumed  to  be  similar 
to  our  own),  yet  atmospheric  disturbances  (due  chiefly,  as  we  know,  to 
these  two  forms  of  action)  could  not  possibly  be  so  violent  even  as  on. 
our  own  earth,  since  corresponding  latitudes  of  Jupiter  (that  is,  regions 
where  corresponding  effects  would  be  experienced)  are  separated  by 
distances  so  very  much  greater.  It  is  clear  that,  if  along  a  certain  zone 
of  a  planet  the  sun  exerts  a  certain  amount  of  influence,  while  along 
another  he  exerts  a  different  influence,  the  result  of  the  difference, 
looked  on  as  a  cause  of  atmospheric  disturbance,  must  be  smaller  as  the 
distance  between  the  zones  is  greater. 


152 


OTHER   WORLDS  THAN   OURS. 


we  add  the  relative  minuteness  of  the  seasonal  changes 
on  Jupiter,  we  see  at  once  that,  unless  some  other  cause 
than  solar  action  were  at  work,  the  condition  of  Jupi- 
ter's atmosphere  ought  to  be  very  much  calmer  than 
that  of  the  earth's. 

It  seems  to  me  that  these  considerations  point  with 
tolerable  clearness  to  the  conclusion  that,  within  the 
orb  which  presents  so  glorious  an  aspect  upon  our 
skies,  processes  of  disturbance  must  be  at  work  wholly 
different  from  any  taking  place  on  our  own  earth. 
That  enormous  atmospheric  envelope  is  loaded  with 
vaporous  masses  by  some  influence  exerted  from  be- 
neath its  level.  Those  disturbances  which  take  place 
BO  frequently  and  so  rapidly  are  the  evidences  of  the 
action  of  forces  enormously  exceeding  those  which 
the  sun  can  by  any  possibility  exert  upon  so  distant  a 
globe.  And  if  analogy  is  to  be  our  guide,  and  we 
are  to  judge  of  the  condition  of  Jupiter  according 
to  what  we  know  or  guess  of  the  past  condition  of  the 
earth  and  the  present  condition  of  the  sun,  we  seem 
led  to  the  conclusion  that  Jupiter  is  still  a  glowing 
mass,  fluid  probably  throughout,  still  bubbling  and 
seething  with  the  intensity  of  the  primeval  fires, 
sending  up  continually  enormous  masses  of  cloud,  to 
be  gathered  into  bands  under  the  influence  of  the  swift 
rotation  of  the  giant  planet.  No  otherwise,  as  it  seems 
to  me,  can  one  explain  the  intense  vitality,  if  one 
may  use  the  expression,  of  a  planet  circumstanced  as 
Jupiter  is.  No  otherwise  can  one  understand  whence 
his  atmosphere  is  loaded  with  vapor-masses  whose 
contents  must  exceed,  on  a  moderate  computation,  all 


JUPITER,  GIANT  OF  THE  SOLAR  SYSTEM.      l<^ 

the  oceans  on  the  surface  of  this  earth.  When  we  see 
masses  so  enormous  swayed  by  influences  of  such 
energy,  that  intermediate  belts,  thousands  of  miles  in 
width,  are  closed  up  in  a  single  hour ;  *  when  we  recog- 
nize the  tremendous  character  of  the  motions  which, 
from  beyond  four  hundred  millions  of  miles,  are  dis- 
tinctly cognizable  by  our  telescopes,  we  see  that  we 
have  no  ordinary  phenomena  to  deal  with,  and  that  the 
theory  we  adopt  for  their  explanation  cannot  be  other- 
wise than  striking  and  surprising. 

If  the  view  which  I  have  here  put  forward — or 
rather,  the  view  to  which  I  have  been  led  by  a  careful 
consideration  of  the  phenomena  which  Jupiter  presents 
to  our  contemplation — be  indeed  correct,  we  must  of 
course  dismiss  the  idea  that  the  giant  planet  is  at  pres- 
ent a  fit  abode  for  living  creatures.  Yet  need  we  not 
turn  from  his  system  with  the  thought  that  here  at 
least  our  hopes  of  recognizing  other  worlds  have  been 
disappointed.  If  Jupiter  be  still  in  a  sense  a  sun,  not 
indeed  resplendent  like  the  great  centre  of  the  planet- 
ary scheme,  but  still  a  source  of  heat,  is  there  not  ex- 
cellent reason  for  believing  that  the  system  which  cir- 
cles around  him  consists  of  four  worlds  where  life — 
even  such  forms  of  life  as  we  are  familiar  with — may 
still  exist  ?  Those  four  orbs,  which  our  telescopes  re- 
veal to  us  as  tiny  points  of  light,  are  in  reality  globes 
which  may  be  compared  with  the  four  worlds  that 

*  Even  if  we  take  the  disappearance  of  a  dark  belt  to  be  due  to  the 
formation  of  clouds,  which  is  perhaps  more  probable  than  that  the  clouda 
of  neighboring  belts  have  closed  in,  the  forces  represented  by  the  change 
tre  nevertheless  tremendous. 


'54 


OTHER    WORLDS  THAN  OURS. 


circle  nearest  to  the  sun.  I  have  shown  that  they  can- 
not subserve  the  purpose  which  many  astronomers 
have  ascribed  to  them,  of  compensating  Jupiter  for 
the  small  amount  of  light  he  receives,  even  if  they 
could  be  seen  from  any  point  of  his  cloud-encom- 
passed surface.  So  that,  even  adopting  the  common- 
place and  superficial  view  that  the  purpose  of  any  ob- 
ject may  be  regarded  as  ascertained  when  we  have 
been  able  to  ask  (without  any  obvious  answer)  what 
other  purpose  it  can  subserve,  we  still  are  led  to  the 
belief  that  the  satellites  of  Jupiter  must  be  the  abode 
of  life,  since  on  this  view,  and  on  this  view  only,  we 
find  a  raison  d'etre  both  for  the  planet  and  for  the  sys- 
tem which  circles  round  him. 

There  are  no  considerations  which  appear  directly 
opposed  to  the  view  that  Jupiter  is  in  a  sense  a  sun. 
It  need  hardly  be  said  that  I  do  not  regard  him  as 
being  in  the  same  condition  as  the  central  luminary 
of  the  planetary  system.  He  is  not  an  incandescent 
body,  or,  if  he  is,  the  greater  part  of  his  light  is  veiled 
by  the  cloud-envelopes  which  surround  him.  The 
solar  clouds  are,  as  we  know,  themselves  luminous ; 
those  of  Jupiter  are  not  so,  a  circumstance  which 
indicates  that  the  heat  of  Jupiter  is  not  sufficient 
to  vaporize  those  substances  which  are  incandescent 
when  in  the  liquid  state.  The  outer  layer  of  clouds 
must,  therefore,  be  regarded  as  for  the  most  part 
aqueous.  We  see  there,  in  fact,  the  future  oceans  of 
Jupiter,  if  the  hypothesis  I  am  now  dealing  with  bo 
correct. 

That  Jupiter  may  supply  an  immense  amount  of 


JUPITER,  GIANT  OF  THE  SOLAR  SYSTEM.      155 

heat  to  his  satellites  (on  this  view  of  his  condition)  is 
perfectly  clear,  since  the  amount  of  light  he  emits  is 
no  adequate  measure  of  the  amount  of  obscure  heat 
which  radiates  from  him  to  the  four  worlds  around 
him.  When  we  consider  the  enormous  apparent,  size 
of  Jupiter  as  seen  from  his  satellites,  we  recognize  at 
once  how  large  a  supply  of  heat  he  is  capable  of  trans- 
mitting to  them.  From  the  outermost  satellite  his 
apparent  diameter  exceeds  that  of  the  sun  (as  seen  by 
us)  some  eightfold,  and  his  apparent  size,  therefore, 
exceeds  the  sun's  more  than  sixtyfold.  From  the 
innermost  he  is  seen  with  a  diameter  nearly  forty  times 
that  of  the  sun,  and  with  an  apparent  area  more  than 
fourteen  hundred  times  as  large  as  his. 

We  have  evidence,  however,  which  renders  it  far 
from  improbable  that  Jupiter  may  emit  some  small 
proportion  of  light.  I  have  already  referred  to  the 
singular  excess  of  his  brilliancy  over  that  due  to  his 
size  and  his  distance  from  the  sun  and  from  us.  The 
estimates  of  Zollner,  the  eminent  photometrician,  serve 
to  show,  not,  indeed,  that  Jupiter  sends  more  light  to 
us  than  he  receives  from  the  sun,  but  that  he  sends 
much  more  light  than  a  planet  of  equal  size  and  con- 
stituted like  Mars,  the  moon,  or  the  earth,  could  possi- 
bly reflect  to  us  if  placed  where  Jupiter  is.  Whereas 
Mars  reflects  but  one-fourth  of  the  light  he  receives, 
Jupiter  reflects  more  than  three-fifths.  The  moon  sends 
less  than  a  fifth  ;  Saturn,  Jupiter's  brother  giant,  more 
than  a  half.  The  late  Prof.  Gr.  Bond,  of  America,  act- 
ually calculated  that  Jupiter  sends  forth  more  light 
than  he  receives.  Whether  his  observations  or  the 


I56 


OTHER    WORLDS  THAN  OURS. 


more  systematic  observations  of  the  German  astron- 
omer are  accepted,  we  see  that,  unless  we  adopt  some 
such  hypothesis  as  I  have  dealt  with  above,  we  must 
recognize  a  marked  difference  between  the  relative 
light-reflecting  capacities  of  the  two  largest  planets  of 
the  system,  and  those  of  Mars  or  the  moon.  In  fact, 
from  other  researches  of  Dr.  Zollner's  it  follows  that, 
if  Jupiter  do  not  shine  in  part  by  native  light,  his  sur- 
face must  possess  reflective  powers  nearly  equal  to  those 
of  white  paper.  Now,  this  would  scarcely  be  credible, 
even  though  under  .the  telescope  the  planet's  surface 
were  found  to  be  universally  white ;  but,  as  we  find  a 
large  proportion  of  it  to  be  of  a  dull  coppery  hue,  we 
seem  forced  to  admit  that  it  cannot  really  have  an  av- 
erage reflective  power  nearly  so  great  as  that  calculated 
by  Zollner.  It  follows,  as  at  least  highly  probable, 
that  Jupiter  shines  in  part  by  his  own  light,  and  this 
being  admitted,  we  cannot  but  regard  it  as  highly 
probable  that  the  mass  of  the  planet  must  be  intensely 
hot. 

It  may  seem,  at  first  sight,  that  the  apparent  black- 
ness of  the  satellites'  shadows,  as  seen  on  the  disk  of 
Jupiter,  is  wholly  opposed  to  the  view  that  any  por- 
tion of  his  light  is  native.  But,  as  a  matter  of  fact, 
there  is  no  force  at  all  in  this  consideration,  or  rather, 
whatever  weight  we  may  attach  to  the  observed  ap- 
pearance of  the  satellites'  shadows  is  in  favor  of  the 
strange  theory  here  put  forward.  For  it  has  been  a 
subject  of  remark  among  the  most  experienced  ob- 
servers, that  a  satellite  in  transit  will  occasionally  ap- 
pear as  dark  as  its  shadow,  both  seeming  black.  The 


JUPITER,  GIANT  OF  THE  SOLAR  SYSTEM.      157 

blackness,  then,  is  only  apparent,  and  an  effect  of  con- 
trast. In  reality,  if  such  observations  as  I  have  men- 
tioned are  to  be  trusted  (and  I  know  no  reason  for  dis- 
regarding them),  the  shadow  of  a  satellite  is  not  black, 
and  therefore  there  seems  no  escape  from  the  conclu- 
sion that  the  surface  on  which  they  are  projected  is 
partially  self-luminous. 

A  stronger  argument  against  the  belief  that  Jupi- 
ter is  self-luminous,  lies  in  the  fact  that  the  satellites 
disappear  in  his  shadow.  It  must  be  remembered, 
however,  that  in  any  case  we  can  assign  but  a  small 
proportion  of  inherent  light  to  Jupiter,  and  that  his 
satellites  would,  therefore,  in  any  case,  lose  so  large  a 
proportion  of  their  light  when  passing  into  his  shadow, 
that  we  might  expect  them  to  disappear,  even  under 
the  closest  telescopic  scrutiny. 

Although  I  have  already  far  exceeded  the  limits  I 
had  proposed  to  myself  for  the  consideration  of  this 
noble  planet,  it  is  with  regret  that  I  take  leave  of  him 
to  pass  onward  to  the  outermost  bounds  of  the  solar 
system.  I  would  fain  dwell  even  longer  than  I  have, 
on  a  subject  of  contemplation  at  once  so  interesting 
and  so  instructive.  Jupiter,  the  centre  of  a  noble  sys- 
tem of  worlds,  or  Jupiter,  himself  a  world,  inhabited 
by  beings  as  high  perhaps  in  the  scale  of  creation  as 
he  himself  is  in  the  scheme  of  the  planets,  is  alike-  a 
worthy  subject  of  study.  The  more  one  dwells  on  the 
features  he  presents,  the  more  one  is  impressed  with 
the  sense  of  the  grandeur  of  his  position  in  the  uni- 
verse. Surely,  whether  now  inhabited  or  not,  he 
must  be  intended  to  be  one  day  the  abode  of  noble 


158  OTHER    WORLDS  THAN  OURS. 

races.  Surely  no  astronomer  worthy  the  name  can 
regard  this  grand  orb  as  the  cinder-centred  globe  of 
watery  matter  so  contemptuously  dealt  with  by  one 
who,  be  it  remembered  thankfully,  was  not  an  as- 
tronomer. He  who  has  not  gazed  hour  after  hour  on 
the  glories  of  the  giant  planet,  gathering  fresh  delight 
as  feature  after  feature  is  revealed  beneath  his  scru- 
tiny— he  who  takes  his  astronomy  but  at  second-hand 
from  the  pages  of  the  real  worker,  turning  from  la- 
bors in  other  fields  "  to  see  what  these  star-gazers  have 
to  say,"  may  lightly  disregard  the  grand  lesson  which 
the  heavens  are  always  teaching,  and  find  only  the 
grotesque  and  the  incongruous,  where  in  reality  there 
is  the  perfectest  handiwork  of  the  Creator.  But  the 
astronomer,  imbued  with  the  sense  of  beauty  and  per- 
fection which  each  fresh  hour  of  world-study  instils 
more  deeply  into  his  soul,  reads  a  nobler  lesson  in  the 
skies.  The  music  which  reaches  his  ears  may  be 
fitful,  but  it  is  not  "  as  sweet  bells  jangled  out  of  tune 
and  harsh ; "  he  may  not  master  its  full  meaning, 
though  every  note  thrills  through  his  inmost  soul ; 
but,  even  when  its  sounds  are  least  distinct,  they  have 
a  beauty  and  solemnity  which  are  all  their  own.  In 
fine,  the  true  astronomer  may  say  with  the  Pythago- 
rean, but  in  another  sense : 

"  There's  not  one  orb  which  thou  behold'st 
But  in  his  motion  like  an  angel  sings, 
Still  quiring  to  the  young-eyed  cherubim ; 
But  while  this  muddy  vesture  of  decay 
Doth  grossly  close  us  in  we  cannot  hear  it." 


CHAPTER  VI. 

SATURN  :    THE   RINGED    WORLD. 

IF  Jupiter  by  his  commanding  proportions  affords 
a  forceful  argument  against  the  view  that  our  tiny 
earth  is  the  only  real  world  in  the  solar  system,  Sat- 
urn supplies  an  argument  of  scarcely  inferior  strength 
in  the  singularly  complex  character  of  the  scheme  of 
which  he  is  the  centre.  !N"o  one  can  contemplate  this 
glorious  planet,  as  shown  by  a  telescope  of  adequate 
power,  without  being  impressed  by  the  conviction  that 
he  is  looking  at  a  world  altogether  more  important  in 
the  scheme  of  creation  than  the  globe  on  which  he 
lives.  Whether  he  recognizes  in  the  present  condi- 
tion of  the  planet  the  result  of  the  action  of  those 
laws  which  the  Almighty  has  assigned  to  His  uni- 
verse, or  whether  he  prefers  the  view  that  Saturn  and 
his  system  are  seen  now  as  they  were  fashioned  at  the 
beginning  by  the  Almighty's  creative  hand,  he  is 
alike  amazed  at  the  wealth  of  design  exhibited  in  the 
ecene  he  is  gazing  upon.  He  may  not  be  able,  in- 
deed, to  appreciate  the  true  character  of  the  purposes 
which  the  various  parts  of  the  Saturnian  system  are 


/6o  OTHER   WORLDS  THAN  OURS. 

intended  to  subserve,  or  he  may,  in  the  rash  attempt 
to  solve  the  mighty  problem,  be  led  to  erroneous  con- 
ceptions; but  that  the  great  planet  is  designed  for 
purposes  of  the  noblest  sort,  he  cannot  gravely  ques- 
tion.* 

In  volume  and  mass  Saturn  is  inferior  to  Jupiter. 
Jupiter  is  twelve  hundred  and  thirty  times,  Saturn  is 
not  quite  seven  hundred  times  as  large  as  the  earth  ; 
and,  while  Jupiter  outweighs  her  three  hundred  times, 
Saturn  is  scarcely  ninety  times  as  heavy  as  she  is. 
Still  Saturn  is  sufficiently  large  and  massive  to  dwarf 
our  earth  to  insignificance;  and  even  Uranus  and 
Neptune,  though  belonging  to  the  family  of  the 
major  planets,  and  giants  compared  with  the  earth, 
fall  below  Saturn  far  more  than  he  does  below  Ju- 
piter. 

Like  Jupiter,  Saturn  rotates  very  rapidly  on  his 
axis,  the  length  of  his  day  being  about  10£  of  our 
hours.  The  materials  of  which  Saturn  is  composed 
have  a  mean  density  not  much  greater  than  half  that 
of  Jupiter,  or  less  than  three-fourths  of  the  mean  den- 
sity of  water.  In  fact,  Saturn's  substance  is  specific- 
ally lighter  than  that  of  any  known  planet.  It  seems 
not  impossible  that  we  have  in  this  relation  some  in- 
dication of  the  true  cause  of  that  complexity  of  detail 
which  the  Saturnian  system  exhibits. 

The  equator  of  Saturn  is  inclined  about  28£  de- 

*  I  know  nothing  better  calculated  to  lead  men  to  choose  astronomy 
as  their  favorite  subject  of  study,  than  the  contemplation  of  the  Satur- 
nian system.  I  can  well  remember  the  sensations  with  which — some 
eight  years  since — I  saw  the  ringed  planet  for  the  first  time.  I  look  on 
that  view  as  my  introduction  to  the  most  fascinating  of  all  the  sciences, 


SATURN:    THE  RINGED    WORLD.  161 

ejees  to  the  plane  in  which  the  planet  moves,  so  that 
his  seasons  (so  far  as  they  depend  on  this  circum- 
stance) closely  resemble  in  character  those  of  the  plan- 
et Mars.  ~fe  occupies  about  29|-  years  in  circling 
once  round  the  sun — this  therefore  is  the  length  of  the 
Saturnian.  year.  His  distance  from  the  sun  is  nearly 
twice  that  of  Jupiter,  and  nearly  ten  times  that  of  the 
earth ;  so  that  the  amount  of  light  and  heat  which 
any  portion  of  his  surface  receives  from  the  sun  is 
about  -^st  part  of  that  received  by  a  similar  portion 
of  the  earth's.  His  orbit  being  somewhat  eccentric, 
however,  there  is  a  considerable  variation  in  this  re- 
spect during  the  course  of  a  Saturnian  year,  insomuch 
that  when  he  is  nearest  to  the  sun  he  receives  more 
light  than  when  in  aphelion  in  the  proportion  of 
about  five  to  four. 

Most  of  the  relations  which  have  to  be  considered 
in  discussing  the  habitability  of  Saturn  have  been 
already  dealt  with  (under  very  similar  conditions)  in 
treating  of  other  planets ;  so  that  I  propose  to  touch 
on  them  very  lightly,  in  order  to  come  more  quickly 
to  those  circumstances  which  distinguish  Saturn  spe- 
cially among  the  other  members  of  the  solar  system. 

Gravity  at  his  equator  is  almost  exactly  equal  to 
gravity  at  the  earth's  surface.  Near  the  poles  there  is 
a  marked  increase  in  the  action  of  Saturnian  gravity, 
insomuch  that  a  body  weighing  ten  pounds  at  his 
equator  would  weigh  about  twelve  pounds  at  either 
pole.  There  is  nothing,  however,  in  this  peculiarity 
which  need  be  specially  dwelt  upon. 

The  length  of  the  Saturnian  year,  and  the  small 


1 62  OTHER   WORLDS  THAN  OURS. 

quantity  of  light  and  heat  received  from  the  sun,  are 
simply  more  market  instances  of  what  has  already 
been  considered  in  the  case  of  Jupiter.  We  may 
conclude  with  some  confidence  that  these  relations  are 
quite  sufficient  to  render  Saturn  wholly  uninhabitable 
by  such  creatures  as  exist  upon  the  earth ;  but  there 
seems  no  reason  for  supposing  that  (so  far  as  these 
relations  alone  are  concerned)  the  planet  may  not  be 
the  abode  of  living  beings  as  high  in  the  scale  of  crea- 
tion as  any  which  live  upon  our  globe. 

And  thus  viewing  Saturn,  we  cannot  regard  even 
the  exceptional  effects  produced  by  his  ring-system  as 
of  themselves  sufficient  to  banish  life  from  his  surface. 
These  effects  are  not  without  interest,  however,  and,  as 
they  have  been  made  the  subject  of  some  discussion,  I 
may  be  permitted  to  make  a  few  remarks  upon  them. 

I  apprehend  that,  when  Sir  John  Herschel  said 
that  the  rings  occasion  an  eclipse  of  nearly  fifteen 
years  in  duration,  first  to  the  northern  and  then  to 
the  southern  hemisphere  of  the  planet,  he  meant  sim- 
ply that  during  an  interval  of  such  length  a  large  por- 
tion of  either  hemisphere  was  in  shadow.  He  knew 
perfectly  well  that,  long  after  the  edge  of  the  ring 
has  been  turned  directly  toward  the  sun,  a  very  large 
proportion  of  the  hemisphere,  over  which  the  ring's 
shadow  proceeds  to  sweep,  remains  illuminated.  It 
had  always  seemed  to  me,  therefore,  altogether  a  mis- 
take on  the  part  of  Dr.  Lardner  to  interpret  Herschel's 
words  as  though  implying  that  a  whole  hemisphere  of 
the  planet  is  eclipsed  for  fifteen  years  in  succession. 

So  misinterpreting  the  expression  used  by  Sir  John 


SATURN:    THE  RINGED    WORLD.  ^ 

Herschel,  Dr.  Lardner,  in  his  desire  to  show  that  no 
such  relation  existed,  was  led  inrtUT  real  mistakes  which 
a  sounder  mathematician  would  not  have  fallen  into. 
He  examined  the  relations  presented  by  the  ring  in  a 
£t#wi-mathematical,  but  inexact  manner,  and  came  to 
the  following  conclusions :  "  That,  by  the  apparent  mo- 
tions of  the  heavens  produced  by  the  diurnal  rotation 
of  Saturn,  the  celestial  objects,  including  the  sun  and 
the  eight  satellites,  are  not  carried  parallel  to  the 
edges  of  the  rings ;  that  they  are  moved  so  as  to  pass 
alternately  from  side  to  side  of  these  edges ;  that,  in 
general,  such  objects  as  pass  under  the  rings  are  only 
occulted  by  them  for  short  intervals  before  and  after 
their  meridional  culmination  (sic) ;  that,  although,  un- 
der some  rare  and  exceptional  circumstances  and  con- 
ditions, certain  objects — the  sun  being  among  the 
number — are  occulted  from  rising  to  setting,  the  en- 
durance of  these  phenomena  is  not  such  as  has  been 
supposed,  and  the  places  of  their  occurrence  are  far 
more  limited."  All  these  statements  are  more  or  less 
incorrect,  and  most  of  them  are  the  direct  reverse  of 
the  truth.  The  seven  inner  satellites  of  Saturn  stand 
in  an  altogether  different  relation,  with  respect  to  the 
rings,  than  all  other  celestial  objects,  since  they  travel 
in  the  same  plane  and  in  circles  concentric  with  the 
outlines  of  the  rings :  they  can,  therefore,  no  more  be 
occulted  by  the  rings,  than  an  outer  ring  can  be 
occulted  by  an  inner  one.  So  far  is  it  again  from  be- 
ing true  that  the  sun  is  in  general  only  occulted  for  a 
short  time  before  and  after  culmination,  that  the  more 
common  case  (considering  the  whole  planet)  is  for  the 


1 64  OTHER    WORLDS  THAN  OURS. 

sun  to  be  eclipsed  (if  at  all)  throughout  the  whole  of 
the  Saturnian  day ;  and  a  very  common  case,  left  al- 
together unnoticed  by  Dr.  Lardner,  is,  that  the  sun  is 
occulted  in  the  forenoon  and  afternoon,  but  free  from 
eclipse  in  the  middle  of  the  day.  Nor  is  it  true  that 
the  places  where  the  sun  can  be  totally  eclipsed 
throughout  the  day  are  limited  to  a  relatively  small 
portion  of  the  planet,  since  every  part  of  the  planet 
whence  the  rings  are  visible  at  all  has  the  sun  eclipsed 
by  the  rings  throughout  the  whole  day  for  a  longer  or 
shorter  succession  of  rotations,  and,  in  the  remaining 
or  polar  regions  of  the  planet,  the  sun  is  altogether 
absent  for  long  intervals  of  time,  for  the  same  reason 
that  he  is  absent  from  the  skies  of  our  polar  regions 
during  a  comparatively  short  interval.  As  for  the 
endurance  of  the  total  diurnal  eclipses,  it  is  only  ne- 
cessary to  remark  that,  in  Saturnian  latitudes  corre- 
sponding to  that  of  London  or  Paris,  the  sun  is  totally 
eclipsed  for  more  than  five  years  in  succession,  while 
in  a  latitude  corresponding  to  that  of  Madrid  he  is 
totally  eclipsed  for  nearly  seven  years  in  succession. 
This  suffices  to  show  that  an  arrangement  which  the 
inhabitants  of  earth  would  find  wholly  unendurable 
prevails  over  a  very  large  proportion  of  Saturn's  sur- 
face.* 

*  The  views  here  expressed  as  to  the  effects  of  the  Saturnian  rings 
are  founded  on  exact  mathematical  calculation,  of  which  the  elements 
are  given  in  my  treatise  on  Saturn.  The  problem  is  not  by  any  means 
a  difficult  one,  and  the  only  way  in  which  the  erroneous  views  formed 
by  Dr.  Lardner  can  be  explained  is,  by  considering  that  he  dealt  with 
the  problem  hi  a  general  instead  of  an  exact  manner.  I  could  not  feel 
any  doubt  as  to  the  accuracy  of  my  results,  but  I  was  not  the  less 
pleased  to  receive  a  letter  from  Mr.  Freeman,  a  Fellow  of  St.  John's 


SATURN:    THE  RINGED   WORLD. 


165 


But,  if  we  consider  the  matter  rightly,  we  shall  see 
that  this,  after  all,  need  not  surprise  us,  since  there  is 
already  in  the  enormous  distance  of  Saturn  from  the 
Bun  the  amplest  reason  for  believing  that  he  cannot 
be  inhabited  by  such  creatures  as  exist  upon  the  earth. 
It  is  in  vain  that,  by  conceiving  him  to  be  surrounded 
by  a  dense  atmosphere,  we  assign  to  him  a  mean 
climate  as  warm  as  that  of  the  earth.  The  want  of 
direct  solar  heat  still  remains,  and  must  be  regarded 
as  a  fatal  objection  to  the  habitability  of  Saturn  by 
races  resembling  those  with  which  we  are  familiar. 

In  the  case  of  Saturn  as  in  the  case  of  Jupiter,  the 
provision  of  satellites,  and  of  the  rings  which  form 
so  glorious  an  object  to  the  astronomer  on  earth,  is 
altogether  inadequate  to  increase  the  supply  of  light 
received  by  the  Saturnians  to  any  such  extent  as  has 
been  imagined.  Those  well-meaning  persons  who 
insist  on  their  own  interpretation  of  the  Almighty's 
designs,  are  singularly  successful  in  overlooking  very 
obvious  difficulties.  If  the  design  of  the  rings,  for  in- 
stance, really  were  to  compensate  the  Saturnians  for  the 
small  amount  of  light  which  they  receive  from  the  sun, 
it  would  surely  follow  that  there  was  a  want  of  wisdom 
in  the  selection  of  an  arrangement  by  which  more  light 
is  kept  away  from  Saturn  than  the  rings  can  possibly 
reflect  to  him.  And  further,  during  the  very  season 
when  the  extra  light  derived  from  the  rings  is  most 
required  by  the  planet,  that  is,  during  the  long  nighta 

College,  Cambridge,  stating  that  he  had  obtained  similar  results,  and 
had  constructed  a  table  on  the  plan  of  Table  XI.  in  my  "Saturn,"  and 
BO  closely  according  with  it  as  not  to  need  separate  publication. 


166  OTHER    WORLDS  THAN  OURS. 

of  the  Saturnian  winter,  they  exhibit  a  dart  band  upon 
the  heavens,  concealing  whole  constellations  from  the 
view  of  the  Saturnian  people.  As  far  as  the  satellites 
are  concerned,  there  is  no  corresponding  difficulty. 
They  undoubtedly  reflect  the  sun's  light  to  Saturn, 
and,  if  there  really  are  intelligent  beings  on  the  planet, 
the  satellites  must  undoubtedly  present  an  interesting 
spectacle,  especially  when  a  large  number  of  the  moons 
are  nearly  full.  But  a  little  consideration  will  show 
that,  even  though  all  the  satellites  were  full  at  the  same 
time,  the  quantity  of  light  they  could  send  back  to 
their  primary  would  be  wholly  inadequate  to  com- 
pensate for  the  planet's  great  distance  from  the  sun. 
According  to  the  best  estimates  of  their  magnitude,  the 
eight  satellites,  taken  in  their  order  from  the  planet, 
cover  spaces  on  the  Saturnian  heavens  which  bear  to 
the  space  covered  by  our  moon  the  respective  propor- 
tions of  about  2,  1,  11  f,  |,  £,  T^,  TV  In  all,  then, 
they  cover  an  area  about  six  times  that  of  our  moon ; 
and  as,  owing  to  their  great  distance  from  the  sun,  they 
are  illumined  by  only  j^^th  of  the  light  which  illu- 
minates our  moon,  they  could  only  send  back  to  the 
planet,  if  it  were  possible  for  them  to  be  all  full 
together,  about  -^th  part  of  the  light  we  receive  from 
the  full  moon.  It  will  be  remembered  that  the  light 
which  could  be  reflected  from  the  Jovial  moons,  if  they 
could  be  all  full  together,  bears  about  the  same  propor- 
tion to  our  moon's.  We  seem  forced  to  the  conclusion 
that  the  satellites  were  intended  to  subserve  no  such 
design  as  has  been  imagined.  Here,  as  in  many  other 
cases,  the  scheme  of  the  Creator  is  not  BO  obvious 


SATURN:    THE  RINGED   WORLD.  167 

to  human  reasoning  as  some  have  complacently  sup- 
posed. 

But  we  have  now  to  consider  peculiarities  which 
suggest  that  Saturn's  globe  has  not  yet  reached  a  con- 
dition fitting  it  to  be  the  abode  of  living  creatures. 
These  peculiarities  resemble  in  great  part  those  which 
have  been  already  noticed  in  the  case  of  Jupiter,  but 
a  certain  most  remarkable  phenomenon  belongs  to 
the  ringed  planet  alone. 

The  belts  of  Saturn  resemble  those  of  Jupiter  in 
their  general  shape  and  also  in  their  color — see  the  ac- 
companying plate.  The  dark  belts  near  the  equator 
are  of  a  faint  brown  or  ruddy  tinge,  those  near  the 
pole  bluish  or  greenish  gray,  while  the  bright  belts  are 
yellowish — the  equatorial  belt  being  the  brightest  of 
all  and  almost  white.  The  poles  are  commonly  dusky 
and  even  sombre  in  hue. 

The  belts  change  in  aspect  much  as  those  of  Jupiter 
have  been  observed  to  do  ;  and  whether  we  regard  the 
change  as  due  to  the  bodily  transference  of  the  belts  of 
cloud  or  to  the  precipitation  of  their  material  in  the 
form  of  rain  (while,  elsewhere,  invisible  vapors  are 
condensed  into  cloud),  we  are  compelled  to  recognize 
the  action  of  forces  altogether  exceeding  those  which 
the  sun  can  be  supposed  to  exert  upon  this  distant 
planet.  The  light  sent  to  us  from  Saturn  also  bears 
a  much  greater  proportion  to  the  amount  of  solar  light 
actually  received  by  the  planet  than  is  observed  in 
the  case  of  Mars  or  the  moon,  and  so  nearly  ap- 
proaches the  proportion  noticed  in  the  case  of  Jupiter 
as  to  lead  to  the  same  inference — namely,  that  a  por- 


X68  OTHER    WORLDS  THAN  OURS. 

tion  of  Saturn's  light  is  emitted  from  the  body  of  the 
planet. 

In  these  respects,  and  also  in  the  small  density  of 
the  planet,  we  seem  to  recognize  evidence  which  points 
to  Saturn  as  probably  a  heat-sun  (if  not  to  any  very 
noteworthy  extent  a  light-sun)  to  the  satellites  which 
circle  round  him,  and  not  himself  the  abode  of  living 
creatures.  Without  dwelling  further  on  evidence 
already  fully  considered  in  the  case  of  Jupiter,  I  turn 
to  one  of  the  most  striking  facts  in  the  whole  range 
of  observational  astronomy,  as  supplying  at  once  new 
evidence  respecting  the  condition  of  Saturn  and 
strengthening  the  evidence  adduced  respecting  Ju- 
piter. 

If  it  can  be  shown  that  Saturn's  globe  is  subject  to 
changes  of  figure  perceptible  even  across  the  enormous 
gap  which  separates  him  from  the  earth,  it  will  at  once 
be  admitted  that  he  can  hardly  be  regarded  as  a  globe 
conveniently  habitable.  Now,  I  have  very  little  hesi- 
tation in  saying  that  evidence  of  the  most  conclusive 
kind  exists  in  favor  of  this  strange  mobility  of  figure. 
It  will  presently  be  seen  that  it  is  with  the  observa- 
tions of  no  mere  amateur  astronomers  that  I  have  to 
deal  in  endeavoring  to  establish  as  a  fact  that  which 
has  commonly  been  spoken  of  as  an  illusion — the  as- 
sumption by  Saturn  of  his  so-called  "  square-shoul< 
dered  "  figure. 

It  was  in  April,  1805,  that  Sir  "William  Herschel 
first  called  attention  to  this  peculiarity.  The  planet, 
which  had  always  presented  to  him  an  elliptical  figure, 
exhibited  a  strangely-distorted  aspect.  A  well-marked 


SATURN:    TEE  RINGED   WORLD.  169 

flattening  at  the  equator,  accompanied  by  an  equally 
well-marked  flattening  at  the  poles,  gave  the  planet's 
globe  an  oblong  figure  (with  rounded  angles),  the 
longest  diameters  having  their  extremities  in  Satur- 
nian  latitude  43°  20' — so  exactly  was  the  great  astron- 
omer able  to  indicate  the  nature  of  the  deformity, 
owing  to  its  well-marked  character. 

What  view  shall  we  form  respecting  an  observation 
of  so  remarkable  a  character  ?  Was  the  peculiarity 
due  to  telescopic  distortion  ?  Herschel  observed  it 
with  several  instruments,  some  seven,  some  ten,  one 
twenty,  and  one  forty  feet  in  length.  Was  the  phe- 
nomenon due  to  atmospheric  disturbances?  Such  dis- 
turbances could  not  account  for  a  persistent  impres- 
sion, however  well  they  might  explain  the  momentary 
assumption  of  the  square-shouldered  aspect  by  the 
ringed  planet.  Besides,  Jupiter  presented  no  such 
appearance.  Was  the  appearance  an  optical  illusion 
due  to  the  position  of  the  ring — then  slightly  open  ? 
If  so,  the  planet  should  always  exhibit  the  square- 
shouldered  aspect  when  his  rings  are  open  to  that  par- 
ticular extent ;  and  this  is  not  the  case.  Besides,  we 
ought  to  notice  a  similar  illusion,  when  looking  at  a 
picture  representing  that  particular  phase  of  Saturn. 
Must  we,  then,  accept  the  astounding  conclusion  that 
the  giant  bulk  of  Saturn  is  subject  to  throes  of  so  tre- 
mendous a  nature  as  to  upheave  whole  zones  of  his 
em-face  five  or  six  hundred  miles  above  their  ordinary 
level  ?  Truly  the  conclusion  is  one  to  be  avoided,  if 
we  can  by  any  possibility  find  a  less  stnrtling  expla- 
nation of  the  matter. 
8 


1 7o 


OTHER   WORLDS  THAN  OURS. 


Yet  where  are  we  to  look  for  sucli  an  explanation  ? 
Was  Sir  William  Herscliel  simply  deceived  ?  I  have 
already  considered  the  general  question  of  illusion, 
but  the  reader  might  entertain  the  explanation  as  con- 
ceivable that  Herschel  might  for  a  while  have  lost  the 
acumen  which  distinguished  him — that  illness,  for  ex- 
ample, might  have  rendered  his  observations  inexact. 
But  we  have  abundant  evidence  that  the  great  astron- 
omer was  in  the  full  possession  of  all  his  wonderful 
powers  as  an  observer  during  the  month  of  April, 
1805  ;  we  know  further  that  by  careful  measurements 
he  rigidly  excluded  all  possibility  of  illusion  affecting 
his  judgment. 

It  would  be  more  satisfactory,  doubtless,  to  the 
reader,  however,  to  learn  that  other  observers  had 
noticed  similar  peculiarities,  or  peculiarities  which,  if 
not  similar,  were  at  least  such  as  to  prepare  us  to 
regard  the  globe  of  Saturn  as  liable  to  remarkable 
changes  of  figure.  Fortunately,  many  such  obser- 
vations have  been  recorded.  I  take  the  following 
from  one  of  an  admirable  series  of  papers  on  Sat- 
urn by  Mr.  Webb,  in  the  Intellectual  Observer  for 
1866. 

On  August  5,  1803,  Schroter  found  Saturn  not 
perfectly  spheroidal  in  figure.  Kitchener  says  that 
for  a  few  months  in  the  autumn  of  1818  he  saw  Saturn 
of  the  figure  described  by  Sir  William  Herschel,  and 
that  with  two  different  achromatics.  At  this  time  the 
ring  must  have  appeared  too  narrow  to  account  for 
the  appearance  as  due  to  illusion.  On  one  occasion 
the  Astronomer  Royal  had  a  similar  view  of  Saturn. 


SATURN:    THE  RINGED    WORLD. 


171 


He  remarks,  also,  that  a  person  unacquainted  with 
Herschel's  observation  remarked  spontaneously  on  the 
flattened  equator  of  the  planet.  On  another  occasion, 
Mr.  Airy  noticed  the  exact  reverse,  the  planet  seem- 
ing flattened  instead  of  upheaved,  in  latitude  45°.  In 
January,  1855,  Coolidge,  using  the  splendid  refractor 
of  the  Cambridge,  U.  S.,  Observatory,  noticed  that  the 
greatest  diameter  of  the  globe  seemed  inclined  about 
20°  to  the  equatorial  diameter ;  but  on  the  9th  the 
equatorial  diameter  seemed  the  greatest ;  while  on  De- 
cember 6th  he  says,  u  I  cannot  persuade  myself  that 
it  is  an  optical  illusion  which  makes  the  maximum 
diameter  of  the  ball  intersect  the  limb  half-way  be- 
tween the  northern  edge  of  the  equatorial  belt  and  the 
inner  ellipse  of  the  inner  bright  ring."  All  this  time 
the  rings  were  nearly  at  their  greatest  opening,  so 
that  any  illusion  should  have  been  of  an  opposite  char- 
acter to  that  observed  when  the  rings  were  nearly 
-closed.  In  the  report  of  the  Greenwich  Observatory 
for  iS60-'61,  it  is  stated  that  "Saturn  has  sometimes 
appeared  to  exhibit  the  square-shouldered  aspect." 
The  eminent  observers  Bond,  father  and  son,  have  no- 
ticed similar  peculiarities,  using  the  great  Merzre  frac- 
tor  already  referred  to.  Each  of  them  noticed  a  flat- 
tening of  the  north-polar  regions  of  the  planet  in  the 
summer  of  1848,  when  the  ring  was  turned  edgewise 
toward  us.  On  the  other  hand,  the  same  observers 
noticed  that  in  1855-'57,  when  the  ring  was  most 
widely  opened,  the  polar  regions  did  not  always  seem 
projected  farthest  on  the  outer  ring  in  a  symmet- 
rical manner,  but  four  times  on  the  left  of  the  polet 


172  OTHER   WORLDS  THAN  OURS. 

once  on  the  right,  and  once  only,  exactly  opposite 
the  pole.  "  The  outline  of  this  region  also  occasion- 
ally appeared  irregularly  flattened  and  distorted,"  an 
appearance  not  satisfactorily  explained  by  the  jux- 
taposition of  the  dark  shadow  of  the  planet  on  the 
ring. 

Now,  there  can  be  no  doubt  whatever  that  the 
planet  Saturn  is  not  ordinarily  distorted.  In  1832, 
during  the  disappearance  of  the  ring,  Bessel  carefully 
determined  the  figure  of  the  planet's  disk,  and  Main 
in  1848  (when  the  ring  was  again  turned  edgewise 
toward  us)  made  similar  measurements.  Each  of 
these  trustworthy  authorities  came  to  the  conclusion 
that  the  disk  of  Saturn  did  not,  at  the  seasons  when 
they  respectively  measured  it,  exhibit  any  distortion 
of  figure  such  as  Herschel  had  described. 

We  seem  almost  compelled,  therefore,  to  accept 
the  conclusion  that  the  planet  Saturn  is  subject  to  the 
influence  of  forces  which  either  upheave  portions  of  its 
surface  from  time  to  time,  or  cause  vast  masses  of 
cloud  to  rise  to  an  enormous  height  above  the  mean 
layer  of  Saturn's  cloud-envelope.  Whichever  view  we 
adopt,  we  cannot  fail  to  recognize  the  fact  that  an  in- 
tense heat  must  in  all  probability  prevail  in  the  great 
globe  of  Saturn ;  and  doubtless  the  real  mass  of  the 
planet  must  emit  a  brilliant  light,  though  the  cloud- 
strata  surrounding  him  may  prevent  us  from  recogniz- 
ing more  than  a  minute  proportion  of  his  luminosity. 
In  fact,  according  to  this  view,  Saturn  and  Jupiter, 
unlike  the  sun,  whose  real  substance  emits  a  less  in- 
tense light  than  the  cloud-photosphere  surrounding  him, 


SATURN:    THE  SINGED   WORLD. 


173 


must  have  nuclei — solid  or  liquid — sinning  with  an 
altogether  more  brilliant  light  than  the  cloud-envel- 
opes of  these  planets  seem  actually  to  emit. 

"Why  Saturn,  rather  than  Jupiter,  should  exhibit 
these  mysterious  changes  of  figure,  is  readily  explica- 
ble when  we  remember  the  near  coincidence  of  the 
planes  in  which  the  Jovial  satellites  move  with  the 
orbital  plane  of  their  primary.  There  thus  always  re- 
sults a  close  agreement  between  the  zone  on  which  the 
satellites  exert  their  greatest  disturbing  influences,  and 
that  most  influenced  by  the  solar  action.  No  such  co- 
incidence exists  in  the  case  of  Saturn,  whose  satellites 
travel  in  a  plane  inclined  nearly  thirty  degrees  to  that 
in  which  their  primary  travels.  It  is  worthy  of  men- 
tion, however,  that  Schroter,  an  accurate  and  practised 
observer,  records  that  on  certain  occasions  he  thought 
he  could  detect  partial  flattenings  of  the  disk  of  Ju- 
piter (see  also  Preface). 

I  think  the  evidence  in  the  case  of  Saturn  favors, 
at  least  as  strongly  as  that  which  has  been  adduced  in 
the  case  of  Jupiter,  the  belief  that  the  giant  planets 
outside  the  zone  of  asteroids  are  not  themselves 
suitable  abodes  for  living  creatures,  but  are  suns,  sup- 
plementing the  small  amount  of  light,  and  yet  more 
fully  supplementing  the  small  amount  of  heat  which 
the  sun  supplies  to  the  satellites  which  circle  around 
these  orbs.  Undoubtedly,  if  we  are  to  judge  accord- 
ing to  the  method  which  has  been  so  often  applied  to 
such  questions,  if  we  are  to  ask  ourselves  according  to 
what  arrangement  the  central  planets  and  the  schemes 
circling  round  them  seem  most  reasonably  interpreted, 


'74 


OTHER   WORLDS  THAN  OURS. 


we  should  at  once  adopt  some  such  conclusion.  For, 
by  taking  Jupiter  and  Saturn  to  be  strictly  analogous 
to  our  own  earth,  and  their  satellites  to  be  subsidiary 
bodies,  resembling  our  moon  in  this,  that  they  sub- 
serve at  present  no  other  purpose  but  to  illuminate 
the  nocturnal  skies  and  to  sway  the  oceans  of  their 
primaries,  we  find  ourselves  perplexed  by  the  consid- 
eration that  a  much  simpler  arrangement  would  have 
subserved  these  purposes  much  more  completely.  In 
the  case  of  Saturn's  satellites,  indeed,  it  seems  diffi- 
cult to  conceive  that  these  bodies  could  have  been  in- 
tended to  fulfil  any  such  purposes,  since  the  two  outer 
ones  could  neither  give  any  useful  light  to  their  pri- 
mary, nor  sway  appreciably  any  oceans  which  may 
exist  upon  the  planet. 

On  the  other  hand,  if  Saturn  and  Jupiter  are  suns 
to  their  satellites,  we  see  in  the  Saturnian  and  Jovial 
systems  real  miniatures  of  the  solar  system.  We  no 
longer  require  that  the  planets  themselves  should  be 
habitable,  any  more  than  we  require  that  our  sun 
should  be  so.  In  fine,  we  do  not  find  in  any  portion 
of  either  system  that  waste  of  material  which  per- 
plexes us  under  the  former  arrangement. 

I  do  not  say  that  this  mode  of  reasoning  has  any 
great  force.  On  the  contrary,  I  am  disposed  to  demur 
to  the  opinion  that  it  is  given  to  man  to  assign  a  rea- 
son for  all  things  which  science  may  reveal  to  him. 
For  reasons  which  seem  to  me  far  more  convincing, 
I  am  led,  however,  to  believe  that  the  two  most  im- 
portant members  of  the  planetary  scheme  must  be  left 
without  inhabitants  for  the  present,  while  in  exchange 


SATURN:    THE  RINGED   WORLD.  175 

I  submit  to  the  contemplation  of  the  curious  twelve 
small  orbs,  constituting  two  miniature  world-systems. 
The  condition  of  these  worlds  will  be  touched  on 
briefly  in  a  separate  chapter. 


CHAPTER  VII. 

TJRANUS   AND   NEPTUNE,    THE   ARCTIC   PLANETS. 

A  CIRCUMSTANCE  which  is  of  great  importance  in 
considering  the  relations  of  the  outer  planets  is  apt  to 
be  lost  sight  of,  owing  to  the  unsatisfactory  manner  in 
which,  in  nearly  all  books  on  astronomy,  the  planetary 
orbits  are  represented.  To  look  at  the  series  of  equi- 
distant and  concentric  circles  representing  the  orbits 
of  the  planets,  who  would  suppose  that,  in  passing 
from  the  orbit  of  Jupiter  to  that  of  Saturn,  a  distance 
five  times  as  great  as  that  which  separates  our  earth 
from  the  sun  has  to  be  traversed  ?  But  the  distance 
separating  Uranua  from  Saturn  is  twice  as  great  even 
as  this  tremendous  gap,  while  Neptune  travels  as  far 
beyond  Uranus  as  Uranus  beyond  Saturn.  Nine  hun- 
dred millions  of  miles  in  width  is  the  enormous  gap  by 
which  the  path  of  Uranus  is  separated  from  that  of  the 
ringed  planet  on  the  inner  side,  and  from  that  of  dis- 
tant Neptune  on  the  outer,  so  that  a  line  equal  to  the 
diameter  of  Jupiter's  orbit  would  barely  suffice  to  reach 
from  Saturn  to  Uranus,  or  from  Uranus  to  Neptune, 
even  when  either  pair  of  planets  are  in  conjunction. 

TVe  know  so  little  of  the  physical  aspect  of  Uranua 


URANUS  AND  NEPTUNE— ARCTIC  PLANETS.    177 

and  Neptune  that  it  is  extremely  difficult  to  form  any 
opinion  as  to  their  condition.  The  two  planets  resem- 
ble each  other  in  size,  each  being  far  smaller  than 
either  of  the  giant  orbs  we  have  lately  been  consid- 
ering. Uranus  has  a  diameter  of  about  33,250  miles ; 
Neptune  is  somewhat  larger,  his  diameter  having  been 
estimated  at  37,250  miles.  The  volume  of  Uranus  is 
74,  the  volume  of  Neptune  105  times  that  of  the 
earth.  Both  planets  exceed  Saturn  in  density ;  for, 
whereas  Saturn's  mean  specific  gravity  is  but 
that  of  Uranus  is  T^ths,  and  that  of  Neptune 
of  the  mean  specific  gravity  of  our  globe.  Thus  each 
planet  has  a  density  nearly  equal  to  that  of  water. 
The  mass  of  Uranus  exceeds  the  earth's  about  12| 
times,  while  that  of  Neptune  is  some  16f  times  as 
great  as  the  earth's.  It  will  be  seen,  therefore,  that 
though  these  two  far-distant  worlds  are  much  less  mas- 
sive than  Jupiter  or  Saturn,  each  of  them  outweighs 
many  times  the  combined  mass  of  the  four  planets 
which  travel  within  the  zone  of  asteroids.  Yet  grav- 
ity on  the  surface  of  these  two  orbs  is  but  about  three- 
fourths  of  terrestrial  gravity. 

The  disk  of  the  sun  as  seen  from  Uranus  is  less 
than  that  which  we  see  in  the  proportion  of  nearly  390 
to  1,  while  the  Neptunians  have  a  sun  only  about  -g^-g-th 
of  ours,  in  apparent  size ;  and  in  these  proportions  the 
solar  light  and  heat  received  by  these  planets  are  re- 
spectively diminished.  So  small  does  the  sun  appear, 
in  fact,  that  to  eyes  such  as  ours  his  orb  could  not 
present  a  disk-like  figure,  but  would  appear  like  an 
exceedingly  brilliant  day-star. 


178  OTHER    WORLDS  THAN  OURS. 

So  far  we  have  found  the  circumstances  of  the  two 
planets  somewhat  similar.  But  we  have  now  to  con- 
sider a  relation  presented  by  Uranus,  which  is  not 
shared  in  by  Neptune.  It  may  be  remarked  that  we 
know  so  little  about  either  planet  that  any  very  care- 
ful consideration  of  their  habitability  would  be  simply 
a  waste  of  labor.  The  evidence  I  am  about  to  adduce, 
however,  in  the  case  of  Uranus,  seems  thoroughly  to 
dispose  of  the  claim  of  this  planet  to  be  regarded  as  a 
world  inhabited  by  creatures  resembling  those  we  are 
acquainted  with  on  earth ;  and,  as  we  cannot  reason- 
ably suppose  Neptune  to  be  inhabited  by  such  crea- 
tures while  Uranus  is  not,  we  may  very  fairly  regard 
the  question  as  disposed  of  for  both  planets,  even 
though  the  relation  dealt  with  is  peculiar  to  Uranus. 

We  know  that  in  the  case  of  Jupiter,  as  in  that  of 
Saturn,  the  position  of  the  plane  near  which  the  satel- 
lites travel  is  nearly  coincident  with  the  plane  of  the 
primary's  equator.  Therefore,  though  no  telescope 
has  yet  exhibited  any  features  on  the  disk  of  Uranus 
which  can  enable  us  to  determine  the  position  of  its 
equator,  we  can  reasonably  infer  from  the  motion  of 
the  satellites  how  the  equator  of  the  planet  is  situated. 

Now,  the  satellites  of  Uranus  travel  in  a  plane  very 
nearly  at  right  angles  to  the  plane  in  which  the  plan- 
et travels.  It  may  be  mentioned  also,  though  not  im- 
portant for  my  present  purpose,  that  they  travel  in  a 
retrograde  direction.  We  conclude,  then,  that  the  axis 
of  Uranus  lies  very  nearly  in  the  plane  wherein  the 
planet  moves  around  the  sun,  and  that  the  planet  ro- 
tates in  such  a  way  around  this  axis  that  the  sun 


URANUS  AND  NEPTUNE— ARCTIC  PLANETS. 


179 


moves  across  the  [Iranian  skies  from  west  to  east,  in- 
stead of  from  east  to  west.  The  latter  relation  is  of  no 
great  importance;  the  former,  however,  involves  re- 
sults which  dispose  at  once,  and  thoroughly,  of  any 
hopes  we  might  entertain  of  discovering  creatures  in 
Uranus  resembling  those  which  inhabit  the  earth. 

The  inclination  of  the  plane  of  Uranus's  equator 
to  the  path  in  which  he  travels  being  about  T6  degrees, 
it  follows  that  the  Uranian  sun  has  a  range  of  about  76 
degrees  on  either  side  of  the  celestial  equator,  during 
the  long  Uranian  year.  Already,  in  considering  the 
seasons  of  Venus,  I  have  dealt  with  a  peculiarity  of 
this  sort ;  but  in  the  case  of  Uranus  the  effects  are  more 
serious.  We  have  only  to  consider  what  would  be  the 
result  of  so  wide  a  range  of  solar  excursion  north  and 
south  of  the  celestial  equator  in  a  latitude  correspond- 
ing to  that  of  London,  to  see  how  importantly  the 
climatic  relations  of  a  planet  like  Uranus,  occupying 
eighty-four  years  in  circling  once  round  the  sun,  must 
be  affected  by  such  a  peculiarity.  We  know  that  in 
the  latitude  of  London  the  sun  reaches  at  noon,  in 
spring  or  autumn,  an  elevation  of  about  38|-  degrees 
above  the  southern  horizon,  that  in  summer  he  passes 
the  meridian  23^-  degrees  higher,  while  in  winter  he 
passes  the  meridian  23£  degrees  lower,  or  only  fifteen 
degrees  above  the  horizon.  But  in  a  similar  Uranian 
latitude,  while  the  sun  would  reach  the  same  meridian 
elevation  in  spring  or  autumn,  he  would  in  summer 
travel  throughout  the  day  in  a  small  circle,  fourteen 
degrees  only  from  the  pole  (raised  of  course  51£  de- 
grees above  the  northern  horizon.  And  obviously, 


l8o  OTHER   WORLDS  THAN  OURS. 

since  the  year  of  the  Uranians  lasts  eighty-four  of  our 
years,  the  continuance  of  the  sun  above  the  horizon 
would  last  for  many  years.*  So  far  there  is  nothing 
to  render  life  in  Uranus  unpleasant,  always  supposing 
the  small  amount  of  light  and  heat  supplied  by  the 
sun  to  be  compensated  by  some  such  atmospheric  ar- 
rangements as  physicists  have  thought  necessary  for 
the  convenience  of  the  more  distant  planets.  But, 
when  we  consider  the  nature  of  the  Uranian  winter, 
we  find  the  circumstances  such  as  no  such  arrangements 
can  be  conceived  to  alleviate.  The  winter  path  of 
the  Uranian  sun,  in  a  latitude  corresponding  to  that 
of  London,  is  just  as  fully  pressed  below  the  horizon  as 
the  summer  path  is  raised  above  it.  At  midnight  the 
sun  is  65£  degrees,  at  nominal  noon  he  is  3Y|-  degrees 
below  the  southern  horizon.  And  as  with  the  summer 
day,  so  with  the  winter  night,  years  elapse  before 
either  comes  to  an  end.  For  upward  of  twenty  years, 
in  a  latitude  corresponding  to  that  of  London,  the 
Uranians — if  there  are  any — never  see  the  small  Ura- 
nian sun.  During  all  this  long  time,  too,  a  sight  even 
is  denied  them  of  all  parts  of  the  solar  system,  interior 
to  the  orbit  of  Uranus  ;  though  this  deprivation  cannot 
be  regarded  as  very  serious  when  it  is  remembered 
that  to  such  eyesight  as  ours  Saturn  could  barely  be 

*  Exact  calculation  applied  to  relations  so  uncertain  as  those  here  in 
question  would  be  out  of  place.  From  a  careful  construction,  however, 
with  76°  as  the  assumed  value  of  the  inclination  of  the  equator  of 
Uranus  to  the  plane  of  his  orbit,  I  find  that  the  sun  would  continue 
above  his  horizon  in  summer  for  about  23^  years.  Of  course,  it  follows 
that  the  sun  would  continue  below  the  horizon  for  an  equally  long 
period  in  winter  I 


URANUS  AND  NEPTUNE— ARCTIC  PLANETS.    181 

visible  from  Uranus,  even  when  most  favorably  situ- 
ated,* while  Jupiter,  always  near  the  sun,  could  only 
be  occasionally  seen,  shining  with  a  light  somewhat 
less  than  a  fiftieth  of  that  which  he  reflects  to  us  when 
in  opposition. 

When  we  consider  other  latitudes,  we  still  find 
Uranus  ill  provided  for  as  respects  his  winter  season. 
In  all  latitudes  nearer  the  pole  than  the  latitude  just 
considered,  the  Uranians  have  winters  lasting  from 
twenty  years  to  upward  of  forty.  In  latitudes  nearer 
the  equator  the  winter  night  is  shorter,  but  we  must 
approach  quite  close  to  the  equator  before  we  reach  a 
latitude  where  the  winter  night  lasts  less  than  a  year 
or  so.  Over  a  belt  extending  about  fourteen  degrees 
on  each  side  of  the  equator  there  is  a  perennial  suc- 
cession of  days  and  nights  never  exceeding  the  full 
duration  of  the  Uranian  diurnal  rotation.  But  we 
must  not  suppose  that  we  have  thus  found  an  Elysian 
zone  in  Uranus.  The  immense  range  of  the  sun's 
excursions  produces  here  also  a  variety  of  seasonal 
changes  which  we  should  find  altogether  unendurable. 
From  a  sun  barely  rising  above  the  horizon  in  winter, 
to  a  sun  which  rises  vertically  overhead  twice  in  the 
course  of  the  Uranian  summer,  is  a  change  which 

*  Admiral  Smyth  speaks  of  Saturn  as  a  fine  morning  and  evening 
star  for  the  Uranians ;  but,  though  Saturn  may  be  visible,  he  can  hardly 
be  a  fine  object.  At  his  elongations  he  is  twice  as  far  from  the  Urani- 
ans as  he  is  from  us  when  in  opposition,  and  further  he  presents  but  a 
half  disk.  His  light  must  in  fact  be  reduced  to  less  than  one-eighth  of 
that  which  he  presents  to  us  when  in  opposition ;  and,  as,  instead  of 
being  on  a  black  sky,  he  must  be  always  seen  from  Uranus  on  a  twilight 
iky,  he  cannot  appear  a  very  fine  object. 


l8z  OTHER   WORLDS  THAN  OURS. 

hardly  accords  with  our  views  of  what  is  desirable  in 
the  progress  of  the  seasons.  At  the  equator  itself 
there  are  in  reality  two  summers,  occurring  at  the 
period  of  the  sun's  passing  the  celestial  equator. 
Here  for  many  years  together  the  sun  passes  day  after 
day  to  a  point  nearly  overhead.  But  then  comes  the 
long  winter,  in  the  heart  of  which  the  sun  rises  barely 
fourteen  degrees  above  the  northern  or  southern  hori- 
zon. By  whatever  arrangement  we  render  the  long 
Uranian  winters  in  this  part  of  the  planet  endurable, 
we  render  the  heat  of  his  long  summers  unendurable  ; 
and  vice  versa,  if  we  conceive  of  atmospheric  relations 
which  would  render  his  summers  pleasing,  we  have 
caused  his  winters  to  be  so  intensely  cold  that  no 
creatures  we  are  familiar  with  could  endure  the  pro- 
longed and  bitter  frosts,  contrasting  so  distressingly 
with  the  imagined  geniality  of  his  summer  weather. 

If  Uranus  be  inhabited  at  all,  then,  it  must  be  by 
creatures  constituted  in  a  very  different  manner  from 
any  with  which  we  are  acquainted.  To  such  crea- 
tures, if  any  among  them  be  gifted  with  intelligence, 
the  heavens,  though  not  adorned  with  planets,  must 
yet  present  an  interesting  subject  of  study.  The  posi- 
tion of  the  pole,  lying  close  by  the  zodiac,  so  that 
among  the  zodiacal  constellations  there  must  be  all 
the  varieties  of  motion  which  we  recognize  in  passing 
from  the  equatorial  to  polar  constellations,  would  lead 
to  a  certain  complexity  in  celestial  charts  and  globes, 
which  would  invite  us  to  the  conclusion  that  the 
Uranians  must  be  capital  mathematicians.  Then 
there  are  certain  astronomical  subjects  of  study  to 


URANUS  AND  NEPTUNE— ARCTIC  PLANETS.    183 

which  their  mathematical  powers  may  be  devoted  per- 
haps more  successfully  than  those  of  our  astronomers. 
For  example,  the  wide  sweep  of  the  planet's  orbit 
would  enable  the  Uranians  to  recognize  a  displace- 
ment of  the  stars  in  the  course  of  the  long  Uranian 
year.  The  star  Alpha  Centauri,  which  only  exhibits 
to  the  terrestrial  observer  an  annual  parallax  of  one 
second,  would  exhibit  to  the  observer  in  Uranus  a  dis- 
placement of  about  the  third  part  of  a  minute.  Other 
stars  would  be  affected  in  like  proportion,  and  per- 
haps the  Uranians  may  thus  be  enabled  to  form  some 
conception  of  that  relation  which  hitherto  has  proved 
too  baffling  a  problem  to  our  astronomers — the  actual 
configuration  of  the  nearer  parts  of  the  sidereal  sys- 
tem. The  Neptunians  would  of  course  be  even  more 
favorably  circumstanced. 

One  difficulty  presents  itself,  however,  in  thus  con- 
sidering the  prospects  of  the  Uranian  and  Neptunian 
astronomers.  The  enormous  length  of  the  year  of 
each  planet  requires  that  either  the  astronomers  in 
Uranus  and  Neptune  should  be  very  long-lived,  or 
that  they  should  be  very  enthusiastic  in  the  cause  of 
science,  to  prosecute  singly  such  observations  as  Hen- 
derson, Olbers,  or  Peters,  have  singly  prosecuted  on 
our  earth.  A  Uranian  who  made  one  set  of  obser- 
vations to  determine  stellar  parallax  when  he  was, 
say,  twenty-five  years  old,  would  have  to  wait  till  he 
had  nearly  reached  the  threescore  years  and  ten  (not 
perhaps  allotted  as  the  span  of  Uranian  life)  before  he 
could  make  the  corresponding  set,  by  comparing  which 
with  the  former  stellar  parallax  was  to  be  determined. 


184  OTHER    WORLDS  THAN  OURS. 

In  Keptune  life  must  be  prolonged  over  the  century 
(unless  the  study  of  observational  astronomy  com- 
mence during  the  babyhood  of  the  ISTeptunians)  in 
order  that  a  complete  set  of  observations  for  determin- 
ing stellar  parallax  should  be  carried  out.  One  cannot 
but  conceive  that  a  certain  sluggishness  must  mark  the 
progress  of  astronomy  in  these  far-off  worlds  under 
such  circumstances.  In  fact,  the  mere  consideration 
that,  after  a  constellation  has  passed  away  from  the 
nocturnal  skies  of  Uranus  or  Neptune,  thirty  or  forty 
years  in  one  case,  and  seventy  or  eighty  in  the  other, 
must  pass  before  the  constellation  again  becomes  fa- 
vorably visible,  suggests  characteristics  of  astronomi- 
cal observation  altogether  different  from  those  we  are 
familiar  with. 

Admiral  Smyth  suggests  that  these  distant  planets 
must  be  convenient  outposts  for  watching  the  ap- 
proach or  recession  of  comets ;  but,  with  all  diffidence, 
I  would  venture  to  point  out  that  the  inhabitants  of 
the  earth  are,  on  the  whole,  more  favorably  situated  in 
this  respect.  Every  large  comet  which  approaches 
tolerably  near  to  the  sun  during  perihelion  passage  is 
as  likely  to  be  seen  as  to  be  missed  by  the  inhabitants 
of  earth;  but  scarcely  one  out  of  a  thousand  such 
comets  would  be  seen  from  Uranus  or  N"eptune,  since, 
to  be  visible,  a  comet  must  approach  the  sun  or  recede 
from  him  along  a  course  passing  tolerably  near  to  the 
particular  position  of  either  planet  at  the  time ;  and 
the  chances  in  the  case  of  any  individual  comet  would 
be  enormously  against  such  a  contingency. 

With  eyesight   such  as  ours  the  Uranians  could 


URANUS  AND  NEPTUNE— ARCTIC  PLANETS.    185 

distinctly  see  Neptune  when  in  opposition,  but  the 
Neptunians  would  be  wholly  unable  to  see  Uranus,  or 
indeed  any  known  planet  of  the  solar  system. 

Perhaps,  though  we  have  very  little  evidence  on 
the  point,  it  will  be  thought  more  reasonable  to  sup- 
pose that  Uranus  and  Neptune  are  suns  to  their  re- 
spective systems  of  satellites,  than  to  imagine  that 
these  two  drearily-circumstanced  planets  are  them- 
selves inhabited.  Their  satellites  cannot  possibly 
compensate,  to  any  noteworthy  extent,  for  the  small 
amount  of  solar  light  or  heat  which  reaches  their 
primaries.  On  the  other  hand,  it  is  not  difficult  to 
conceive  that  the  planets  may  afford  an  important 
supply  of  heat  (at  any  rate)  to  their  dependent  orbs. 
Certainly,  so  far  as  the  evidence  we  have  extends, 
Uranus  and  Neptune  resemble  Saturn  and  Jupiter  too 
closely  not  to  warrant  the  application  of  any  argu- 
ments deduced  from  the  appearance  of  the  two  giant 
planets  to  the  case  of  their  inferior  but  still  gigantic 
brethren. 

Viewing  the  matter  thus,  we  seem  led  to  the  con- 
clusion that  the  planets  which  lie  outside  the  zone  of 
asteroids  are  distinguished  from  those  within  that  belt, 
not  merely,  as  had  so  long  been  recognized,  in  the 
attributes  of  size,  density,  rapidity  of  rotation,  and 
complexity  of  the  systems  circling  round  them,  but  in 
this  more  important  and  more  interesting  circum- 
stance, that  they  and  their  dependent  orbs  are  real 
miniatures  of  the  solar  system.  Four  suns  they  would 
seem  to  be,  not  indeed  suns  resplendent  like  the  pri- 
mary sun  round  which  they  travel,  but  still  giving  out 


!86  OTHER    WORLDS   THAN  OURS. 

perhaps  no  insignificant  supply  of  light ;  not  heated 
to  incandescence  as  he  is,  but  still  supplying  an 
amount  of  heat  proportionately  far  greater  than  the 
quantity  of  light  they  give  forth :  in  fine,  not,  as  he  is 
to  the  inner  planets,  the  sole  source  whence  all  sup- 
plies of  force  are  derived,  but  adding  their  influence 
to  his  in  a  variety  of  complicated  but  doubtless  well- 
ordered  combinations,  in  such  sort  that  the  small 
worlds  which  circle  around  them  are  provided  with  all 
that  is  needful  to  the  well-being  of  their  inhabitants. 


CHAPTER  YIII. 

THE   MOON   AND   OTHER   SATELLITES. 

ALTHOUGH  I  do  not  think  that  the  moon  can  be  re- 
garded as  probably  at  present  the  abode  of  life,  there 
are  many  reasons  for  studying  in  a  work  on  other 
worlds  the  various  relations  she  presents  to  us.  In 
the  first  place,  she  subserves  various  useful  purposes 
in  the  economy  of  our  own  earth ;  then  there  are  cir- 
cumstances in  her  appearance  which  suggest  that  at 
one  time  there  may  have  been  life  upon  her  surface ; 
and,  lastly,  she  affords  us  the  only  information  we 
have  concerning  the  probable  relations  presented  by 
the  noble  systems  of  moons  which  circle  around  Jupi- 
ter and  the  other  planets  outside  the  orbit  of  the 
asteroids. 

Now,  with  regard  to  the  present  habitability  of  the 
moon,  it  may  be  remarked  that  we  are  not  justified  in 
asserting  positively  that  no  life  exists  upon  her  sur- 
face. Life  has  been  found  under  conditions  so  strange 
— we  have  been  so  often  mistaken  in  assuming  that 
here  certainly,  or  there,  no  living  creatures  can  possi- 
bly exist — that  it  would  bo  rash  indeed  to  dogmatize 
respecting  the  state  of  the  moon  in  this  respect. 


1 88  OTHER   WORLDS  THAN  OURS. 

Still,  in  the  case  of  tlie  moon  we  have  relations 
wholly  different  in  character  from  those  we  have 
hitherto  had  to  consider.  We  no  longer  have  to  deal 
with  a  question  of  the  various  degrees  of  heat  and 
cold,  of  atmospheric  rarity  or  density,  and  the  like, 
but  with  relations  which  do  not  in  the  slightest  degree 
resemble  those  we  are  familiar  with  on  earth. 

In  the  first  place,  the  moon  has  no  appreciable 
atmosphere.  "We  have  long  known  this  quite  certain- 
ly, because  we  see  that  when  stars  are  occulted  by  the 
moon  they  disappear  instantaneously,  whereas  we 
know  this  would  not  be  the  case  had  the  moon  an  at- 
mosphere of  appreciable  extent.  But  if  any  doubt 
could  have  remained,  the  evidence  of  the  spectroscope 
in  Mr.  Huggins's  hands  would  have  sufficed  to  remove 
it.  He  has  never  been  able  to  detect  a  sign  of  the 
existence  of  any  lunar  atmosphere,  though  Mars  and 
Jupiter,  so  much  farther  from  us,  have  afforded  dis- 
tinct evidence  respecting  the  atmospheres  which  sur- 
round their  surface. 

Then,  secondly,  there  are  no  seas  or  oceans  on  the 
moon.  Were  there  any  large  tracts  of  water,  the 
tremendous  heat  to  which  the  moon  is  subjected  dur- 
ing the  course  of  the  long  lunar  day  (lasting  a  fort- 
night of  our  time)  would  certainly  cause  enormous 
quantities  of  water  to  evaporate ;  and  not  only  would 
the  effects  of  this  process  be  distinctly  recognizable 
by  our  telescopists,  but  the  spectroscope  would  exhibit 
in  an  unmistakable  manner  the  presence  of  the  aque- 
ous vapor  thus  formed. 

Thirdly,  there  are  no  lunar  seasons.     The  inclina- 


THE  MOON  AND   OTHER  SATELLITES.          189 

tion  of  the  moon's  axis  to  the  orbit  in  which  she 
travels  round  the  snn  is  nearly  89°,  and  with  this  in- 
clination there  can  be  no  appreciable  seasonal 
changes. 

Fourthly,  the  enormous  length  of  the  lunar  day  is 
altogether  opposed  to  our  conceptions  of  what  is  suit- 
able for  animal  or  vegetable  life.  The  lunar  day  lasts 
about  a  fortnight,  and  the  lunar  night  is,  of  course, 
equally  long.  Were  this  all,  the  inconvenience  of  the 
arrangement  would  be  unbearable  by  beings  like  our- 
selves. But  far  more  serious  consequences  must  result 
from  the  combination  of  the  arrangement  with  the 
want  of  an  atmosphere  ;  for  whereas  during  the  lunar 
day  the  surface  of  the  moon  is  exposed  to  an  incon- 
ceivably intense  direct  heat,  undoubtedly  sufficient  to 
heat  that  surface  far  above  the  boiling  point,  during 
the  lunar  night  the  heat  is  radiated  rapidly  away  into 
space  (no  atmosphere  checking  the  process),  and  an 
intensity  of  cold  must  prevail  of  which  we  can  form 
but  imperfect  conceptions.* 

The  mere  fact  that  our  earth  is  always  invisible 

*  The  moon's  physical  habitudes  are  in  fact  so  very  different  from 
those  of  the  earth  that  one  cannot  read  without  astonishment  the  well- 
known  passage  in  which  Sir  W.  Herschel  pleads  for  the  moon's  habita- 
bility.  "  Its  situation,  with  respect  to  the  sun,"  he  says,  "  is  much  like 
that  of  the  earth,  and  by  a  rotation  on  its  axis  it  enjoys  an  agreeable 
variety  of  seasons  (!)  and  of  day  and  night.  To  the  moon,  our  globe 
will  appear  to  be  a  very  capital  satellite,  undergoing  the  same  regular 
changes  of  illumination  as  the  moon  does  to  the  earth.  The  sun,  the 
planets,  and  the  starry  constellations  of  the  heavens,  will  rise  and  set 
there  as  they  do  here,  and  heavy  bodies  will  fall  on  the  moon  as  they 
do  on  the  earth.  TJiere  seems  only  (o  be  wanting,  in  order  to  complete  th« 
analogy,  that  it  should  be  inhabited  like  the  earth."  The  evidence  is,  how. 
ever,  all  the  other  way. 


I  go  OTHER   WORLDS  THAN  OURS. 

to  three-sevenths  of  the  moon's  surface  is  one  which 
points  very  strongly  to  the  conclusion  that  the  present 
condition  of  the  moon  is  not  the  one  best  calculated 
to  meet  the  wants  of  living  creatures  on  her  surface. 
In  long-past  ages,  when  her  rotation  had  not  yet  been 
forced  into  accordance  with  her  revolution  *  (as  at 
present),  the  earth  must  have  subserved  a  variety  of 
most  important  purposes.  If  water  then  existed  on 
the  surface  of  the  moon,  the  earth  must  have  raised 
tidal  waves  in  her  oceans.  She  must  further  have 
reflected  enormous  supplies  of  light  and  heat  toward 
her  dependent  orb,  even  if  at  that  time  she  were  not 
a  secondary  sun  for  the  lunarians.  She  must  have 
travelled  across  the  lunar  skies  as  the  moon  travels 
over  ours,  presenting  a  variety  of  interesting  and  beau- 
tiful phases  affording  useful  time-measures,  and  so 
enabling  the  travellers  on  the  moon  in  those  long-past 
ages  to  guide  their  course  in  safety  over  her  oceans  or 
her  deserts.  But  now  she  is  invisible  from  a  large 
portion  of  the  moon's  surface,  and  almost  a  fixture  in 

*  The  researches  of  Adams  into  the  peculiarity  of  the  moon's  motion, 
called  her  acceleration,  suffice  to  show  that,  under  the  influence  of  the 
moon's  attraction  on  our  oceans,  the  earth's  rotation  is  gradually  dimin- 
ishing ;  so  that,  though  many  millions  of  ages  must  elapse  first,  she  will 
one  day  so  rotate  as  to  keep  always  the  same  face  turned  toward  her 
satellite.  We  cannot  doubt  that  it  has  been  by  a  process  of  this  sort 
that  the  moon's  rotation  has  been  brought  to  its  present  rate.  In  fact, 
independently  of  the  evidence  afforded  by  the  earth's  gradual  loss  ol 
rotation,  we  cannot  account  for  the  moon's  peculiarity  of  rotation  with 
out  regarding  it  as  due  to  the  earth's  controlling  influence.  A  perfectly 
homogeneous  sphere,  started  on  a  direct  line  at  the  moon's  distance,  and 
with  the  same  velocity,  would  travel  without  rotation  on  an  orbit  like 
the  moon's,  and  would  thus  in  completing  a  revolution  exhibit  every 
part  of  its  surface  to  us. 


THE  MOON  AND    OTHER  SATELLITES.          i9l 

the  skies  of  those  parts,  even,  of  the  moon  whence  she 
can  be  seen.  Were  there  lunar  oceans,  she  could  raise 
no  tides  in  them.  Were  there  a  lunar  atmosphere, 
she  could  shed  no  heat,  to  be  garnered  up,  so  to  speak, 
by  that  atmosphere,  and  to  compensate,  in  some  sort, 
for  the  long  absence  of  the  sun. 

But  have  we  evidence  that  at  some  far-distant 
epoch  the  moon  was  inhabited  ?  Taking  for  our  guid- 
ance the  analogies  which  are  available  to  us,  can  we 
really  conclude  that  once,  in  all  probability,  those  bar- 
ren wastes  were  clothed  with  vegetation,  those  dreary 
solitudes  the  abode  of  life  ? 

When  we  contemplate  with  attention  the  lunar 
surface,  considering  the  indications  it  presents  of  past 
activities,  we  are  led  to  inquire  how  the  forces  which 
have  been  so  busily  at  work  were  expended.  If  Na- 
ture, studied  thoughtfully,  teaches  us  the  lesson  that 
there  is  no  form  of  force  which  is  not  the  representa- 
tive of  some  other  preacting  form  of  force,  she  also 
teaches  us  that  no  form  of  force  ever  works  without 
generating  other  forces  as  its  own  energies  are  expend- 
ed. The  meteor  which  sweeps  with  planetary  velo- 
city through  space  may  be  brought  to  rest  upon  the 
gun,  but  the  energy  stored  up  in  its  motions  is  not 
wasted ;  the  sun  may  expend  the  stores  of  force  he 
derives  from  meteoric  impact,  but  not  idly ;  *  all 

*  The  question  may  be  asked,  What  becomes  of  the  immense  sup- 
plies of  light  and  heat  continually  poured  by  the  sun  and  other  stara 
into  space  ?  We  cannot  tell ;  yet  we  know  certainly  that  they  cannot 
be  wasted.  The  heat  of  Arcturus,  measured  by  Mr.  Stone,  gives  an  ac- 
count of  one  large  portion  of  the  stellar  heat-supplies,  because  we  know 
that,  small  as  the  amount  we  receive  may  be,  we  must  multiply  that 


192 


OTHER    WORLDS  THAN  OURS. 


round  us  we  see  the  fruits  of  solar  energies,  we  feel 
them  within  ourselves,  we  exert  them  upon  others. 
And,  therefore,  when  we  see  on  the  moon  signs  that 
her  surface  was  at  one  time  upheaved  by  tremendous 
volcanic  forces,  we  are  led  to  the  conclusion  that  be- 
tween the  era  when  she  was  thus  disturbed,  and  the 
present  time,  when  she  seems  absolutely  quiescent, 
there  must  have  been  a  period  when  her  energies  were 
employed  in  sustaining  various  forms  of  life.  There 
has,  in  this  instance,  been  a  process  resembling  ex- 
haustion, though  we  know  the  forms  of  force  which 
have  passed  away  from  the  moon  have  not  really 
ceased  to  exist ;  but  before  the  lunar  forces  were  dis- 
sipated into  space,  so  to  speak,  they  must  have  sub- 
served that  great  purpose  which  seems  the  end  of  all 
Nature's  workings — the  support  of  life. 

Associated,  however,  with  this  subject,  there  are 
questions  of  a  perplexing  character,  which  invite  our 
careful  consideration.  If  life  ever  existed  on  the 
moon,  that  orb  must  have  possessed  an  atmosphere 

amount  millions  on  millions  of  times  to  get  the  total  received  by  all  the 
orbs  in  space  from  this  particular  sun.  But  we  know  that  a  large  por- 
tion of  our  sun's  light  and  heat  must  either  fail  to  fall  on  any  other  orbs, 
or  must  be  gradually  exhausted  in  its  progress  through  space  (for,  if 
lines  from  the  sun  in  every  direction  encountered  orbs,  the  sky  ought  to 
be  lighted  up  at  all  times  with  star-splendor — which  is  no  other  than 
sun-splendor).  In  either  case  we  cannot  tell  what  becomes  of  the  por- 
tion seemingly  wasted,  though  in  the  latter  case  we  may  affirm  confi- 
dently that  there  is  simply  a  change  in  the  nature  of  the  force.  In  both 
cases  we  know  that  the  total  of  force  in  the  universe  remains  unditnin- 
ished.  There  is,  indeed,  a  seeming  contradiction  here ;  but  it  is  not  dif- 
ferent in  character  from  the  seeming  contradictions  suggested  by  the 
consideration  of  infinite  space  and  infinite  tune,  which  yet  we  are  com- 
pelled to  recognize  as  absolutely  as  finite  space  or  finite  tune. 


THE  MOON  AND   OTHER  SATELLITES.          193 

and  seas.  Independently,  also,  of  our  views  on  the 
subject  of  life  upon  the  moon,  we  are  led,  by  the  reve- 
lations of  the  spectroscope  respecting  the  solar  system, 
to  believe  that  all  the  bodies  within  that  system  are  in 
a  general  sense  similarly  constituted ;  and,  if  this  be 
BO,  there  must  once  have  been  oceans  and  air  upon  the 
moon.  What  has  become  of  the  moon's  atmospheric 
envelope,  and  of  the  lunar  oceans  ? 

In  four  several  ways  this  question  has  been  an- 
swered. Some  have  thought  that  the  oceans  and  air 
have  been  withdrawn  into  cavities  within  the  moon's 
substance.  Others  have  imagined  that  the  air  and 
oceans  may  have  passed  away  to  the  farther  hemi- 
sphere of  the  moon.  According  to  a  third  theory,  a 
comet  has  carried  off  the  lunar  oceans  and  atmosphere. 
And,  lastly,  a  fourth  theory  has  been  maintained,  ac- 
cording to  which  the  lunar  air,  and  a  fortiori  the 
lunar  seas,  have  been  changed  by  intensity  of  cold  into 
the  solid  form. 

Of  these  theories,  the  first  and  last  only  seem 
worthy  of  consideration.  We  see  so  much  of  the 
moon's  farther  hemisphere  during  her  librations  that 
we  must  perforce  reject  the  second,  even  if  we  had 
any  trustworthy  analogy  for  believing  so  strange  an 
arrangement  to  be  possible.*  The  third  theory  is  op- 

*  Prof.  Newcombe,  of  America,  has  shown  excellent  reasons  for 
doubting  whether  even  that  displacement  of  the  moon's  gravity,  on 
which  the  theory  has  been  based,  can  be  admitted  as  an  established 
fact  Independently  of  this,  however,  the  theory  will  not  bear  exami- 
nation. Any  one  who  will  draw  a  cross-section  of  the  moon  (in  a  plane 
passing  through  the  earth),  and  endeavor  to  assign  such  a  position  to 
an  atmosphere  of  moderate  extent  that,  even  during  the  moon's  extreme 
9 


!94  OTHER    WORLDS  THAN  OURS. 

posed  by  all  that  modern  astronomy  teaches  respect- 
ing the  constitution  of  comets. 

The  theory  that  an  atmosphere  formerly  surround- 
ing the  moon  has  passed  with  the  lunar  oceans  into 
the  interior  of  our  satellite  has  been  supported  by 
physicists  of  considerable  eminence.  The  relatively 
low  specific  gravity  of  the  moon  (little  more  than  half 
the  earth's)  suggests  the  possibility  that  cavities  largo 
enough  to  contain  even  all  the  waters  of  our  own 
oceans  may  exist  within  the  moon.  Nor  does  the  fact 
that  we  can  see  no  unmistakable  signs  of  chasms  ex- 
tending deep  into  the  moon's  substance  suffice  to  ren- 
der the  theory  untenable,  or  even  improbable.  It  is 
difficult  to  understand  how  the  inrush  of  the  waters 
took  place.  Certainly  it  cannot  have  happened  while 
the  moon's  volcanic  forces  were  in  vigorous  action; 
yet  a  period  must  undoubtedly  have  arrived  when  by 
little  and  little  the  waters  could  retire  within  the 
moon's  substance  without  being  vaporized.  From 
what  we  know  of  volcanic  action  on  the  earth,  the 
lunar  volcanoes  must  have  drawn  fresh  supplies  of 
energy  from  the  gradual  influx  of  water  ;  and  one  can 
thus  understand  why  the  aspect  of  the  moon  indicates 
that,  up  to  the  last  moment,  so  to  speak,  of  her  exist- 
ence as  a  world,  the  forces  upheaving  her  crust  were 
busily  at  work.  "We  can  thus  see  how  it  has  come  to 
pass  that  the  moon's  surface  shows  so  few  signs  of  the 
action  of  rain  or  running  water. 

The  theory  that  the  lunar  oceans  have  become 

Iterations,  no  signs  of  the  atmosphere  could  be  perceptible  from  the 
earth,  will  at  once  see  that  the  theory  is  untenable. 


THE  MOON  AND    OTHER  SATELLITES. 


'95 


frozen,  and  that  afterward  even  the  gases  forming  the 
lunar  atmosphere  have  become  solidified,  was  main- 
tained by  Buffon  and  Bailly  in  the  last  century,  and 
has  been  supported  by  several  astronomers  in  our  own 
day.  In  some  respects,  the  aspect  of  the  moon 
(especially  the  absence  of  well-marked  colors  from 
her  surface)  seems  to  favor  the  theory.  Nor  need 
the  excessive  heat  to  which  the  moon's  surface  is 
exposed  for  weeks  at  a  time  be  considered  a  sufficient 
reason  for  rejecting  it,  because  we  have  no  means  of 
judging  how  that  heat  would  act  where  there  is  no 
atmosphere  to  prevent  its  immediate  and  entire  reflec- 
tion into  space.  "We  know  that,  despite  the  intense 
heat  which  is  poured  upon  the  summits  of  the  Hima- 
layas, the  snow  there — though  a  portion  may  melt 
during  the  day — remains  year  after  year  and  age  after 
age  undiminished ;  and  on  the  summit  of  the  Hima- 
layas the  atmosphere  is  dense  and  heavy  compared  with 
that  which  exists  even  in  the  lowest  abysms  of  the  lunar 
ravines.  If  absolute  reliance  be  placed  on  the  results 
which  have  been  deduced  from  the  application  of  the 
great  Parsonstown  mirror  to  the  measurement  of  the 
lunar  heat,  it  would  seem  as  though  we  must  abandon 
the  belief  in  the  existence  of  frozen  oxygen  or  nitrogen 
on  the  moon's  surface,  since,  according  to  those  re- 
salts,  a  large  proportion  of  the  moon's  heat  is  radiant 
— in  other  words,  the  moon's  surface  has  been  actually 
raised  to  a  high  degree  of  heat  by  the  solar  rays.  At 
present,  however,  physicists  are  not  prepared  to  look 
with  perfect  confidence  on  the  method  by  which,  in  the 
researches  made  at  Parsonstown,  an  attempt  has  been 


196  OTHER   WORLDS  THAN  OURS. 

made  to  distinguish  between  the  heat  which  the  moon 
reflects  and  that  which  she  radiates  into  space. 

On  the  whole,  however,  the  former  theory  seems  to 
have  the  strongest  evidence  in  its  favor,  or  rather  the 
least  decisive  evidence  against  it. 

In  considering  the  systems  of  bodies  which  circle 
around  the  outer  planets,  we  are  struck  at  once  by 
several  marked  circumstances  of  contrast  between  their 
condition  and  that  of  our  own  moon. 

In  the  first  place,  we  have  no  satisfactory  evidence 
that  the  satellites  of  Jupiter  and  Saturn  turn  always 
the  same  face  toward  their  primary.  It  is  true  that 
Sir  William  Herschel  was  led  by  certain  observations 
of  the  satellites  of  Jupiter  to  conclude  that  this  relation 
holds  in  their  case.  But  we  have  far  stronger  evidence 
against  such  a  view,  in  the  fact  that  modern  observers, 
armed  with  telescopes  of  the  most  exquisite  defining 
powers,  have  not  only  been  unable  to  confirm  the  rela- 
tively rough  observations  made  by  Herschel,  but  have 
noticed  peculiarities  of  appearance  only  explicable  by 
the  theory  that  the  rotation  of  the  satellites  is  quite  in- 
dependent of  their  motion  of  revolution  around  Jupiter. 
Dawes,  for  instance,  has  observed  that  the  markings 
seen  on  the  third  satellite,  when  transiting  Jupiter's 
disk,  are  variable.  Bond  has  seen  this  satellite  as  a 
well-defined  black  spot  on  certain  occasions,  while  on 
others  it  has  appeared  quite  bright  on  the  disk  of  the 
planet.  He  once  saw  this  satellite  bright  as  it  entered 
on  the  disk  of  Jupiter,  and  about  half  an  hour  later  as 
a  dark  spot ;  while  Mr.  Prince,  with  a  powerful  re- 
flector, has  seen  the  satellite  dark  first  and  afterward 


THE  MOON  AND   OTHER  SATELLITES.          igj 

bright.  It  need  hardly  be  said  that,  if  the  satellite 
turned  always  the  same  face  toward  its  primary,  no 
such  varieties  of  appearance  would  be  presented  dur- 
ing transit.  The  following  passage  from  Webb's  "  Ce- 
lestial Objects  "  points  strongly  also  to  the  conclusion 
that  the  rotation  of  the  Jovial  satellites  must  be  inde- 
pendent of  their  revolution.  After  mentioning  that 
the  variable  light  of  the  satellites  may  be  caused  by 
the  existence  of  spots  upon  their  surface,  he  proceeds  : 
"  A  stranger  source  of  anomaly  has  been  perceived — 
the  disks  themselves  do  not  always  appear  of  the  same 
size  or  form.  Maraldi  noticed  the  former  fact  in  1707, 
Herschel  ninety  years  afterward  inferring  also  the 
latter,  and  both  have  since  been  confirmed.  Beer  and 
Madler,  Lassell  and  Secchi,  have  sometimes  seen  the 
disk  of  the  second  satellite  larger  than  that  of  the  first ; 
and  Lassell,  and  Secchi  and  his  assistant,  have  dis- 
tinctly seen  that  of  the  third  satellite  irregular  and 
elliptical ;  while,  according  to  the  Eoman  observers, 
the  ellipse  does  not  always  lie  the  same  way." 

It  will  easily  be  seen  that  these  peculiarities  indi- 
cate the  existence  of  dark  markings  on  these  bodies, 
and  that,  as  the  satellites  rotate,  the  varying  position 
of  these  markings  causes  the  satellites  seemingly  to 
change  in  figure,  since  the  brighter  part  of  the  satellite 
would  be  that  which  would  determine  its  apparent 
figure.  And  further,  since  the  change  of  figure  shows 
no  correspondence  with  the  position  of  the  satellites 
in  their  revolution,  we  infer  that  their  revolution  is 
independent  of  their  rotation. 

It  is  worthy  of  notice,  however,  that  even  if  the 


I98  OTHER  WORLDS  THAN  OURS. 

inner  satellites  turned  always  the  same  face  toward 
their  primary,  the  peculiarity  would  not  (as  in  the  case 
of  our  moon)  result  in  an  inordinate  lengthening  of 
their  diurnal  period,  since  Jupiter's  two  inner  satellites 
complete  a  revolution  in  one  day  eighteen  and  a  half 
hours,  and  three  days  thirteen  hours  respectively; 
while  the  revolutions  of  Saturn's  five  inner  satellites 
are  severally  accomplished  in  twenty-two  and  a  half 
hours,  one  day  nine  hours,  one  day  twenty-one  hours, 
two  days  eighteen  hours,  and  four  days  twelve  and  a 
half  hours. 

So  far  as  we  can  judge  from  Laplace's  estimates, 
the  specific  gravity  of  Jupiter's  moons  must  be  very 
small  indeed,  ranging  from  one-ninth  to  four-fifths  of 
the  specific  gravity  of  water.  But  very  little  reliance 
can  he  placed  on  these  results,  because  the  only  evidence 
we  have  respecting  the  mass  of  the  satellites  is  that 
founded  on  the  perturbations  to  which  their  motions 
are  subjected,  and  it  is  very  difficult  indeed  to  estimate 
these  perturbations.  When  to  this  we  add  the  cir- 
cumstance that  little  reliance  can  be  placed  on  meas- 
urements of  the  minute  disks  presented  by  the  satel- 
lites, it  will  be  seen  that  our  estimate  of  the  specific 
gravities  of  these  bodies  cannot  by  any  means  be 
regarded  as  trustworthy. 

As  seen  from  his  satellites,  Jupiter  must  present  a 
magnificent  scene.  To  the  inhabitants,  if  such  there 
be,  of  the  innermost  satellite,  he  exhibits  a  disk  nearly 
twenty  degrees  in  diameter.  Thus,  whereas  there 
might  be  about  seven  hundred  moons  such  as  ours 
placed  all  round  our  horizon,  the  disk  of  Jupiter,  as 


THE  MOON  AND    OTHER  SATELLITES. 


199 


eeen  from  the  inner  satellite,  could  occupy  a  full 
eighteenth,  part  of  the  horizon's  circumference.  The 
disk  of  Jupiter,  as  so  seen,  would  cover  a  space  on  the 
heavens  exceeding  more  than  fourteen  hundred  times 
that  which  our  moon  covers.  To  the  second  satellite, 
Jupiter  presents  a  disk  about  12|-  degrees  in  diameter, 
or  about  six  hundred  times  as  large  as  our  moon's. 
To  the  third  satellite  he  shows  a  disk  about  7f  degrees 
in  diameter,  or  more  than  two  hundred  times  the  size 
of  the  moon's.  And,  lastly,  the  inhabitants  even  of 
the  farthermost  satellite  see  him  with  a  diameter  of 
about  4^-  degrees — that  is,  with  a  disk  more  than  sixty- 
five  times  as  large  as  that  of  our  moon.  So  that,  if 
the  views  I  have  put  forward  respecting  Jupiter  be 
correct,  the  enormous  space  he  covers  on  the  skies  of 
his  respective  satellites  must  suffice  to  compensate  in 
part  for  the  relatively  small  amount  of  heat  which  he 
can  be  supposed  capable  of  emitting. 

If  the  satellites  rotate  with  a  motion  independent 
of  their  revolution,  Jupiter  passes  across  their  skies 
like  a  vast  moon,  exhibiting  phases  such  as  those  pre- 
sented by  ours,  but  on  a  far  vaster  scale.  But,  besides 
his  phases,  he  must  exhibit  to  the  inhabitants  of  his 
satellites  the  most  marvellous  picture  that  can  be  con- 
ceived. His  belts'  changes  of  figure  and  color,  only 
rendered  visible  to  our  astronomers  by  powerful  tele- 
scopic aid,  must  be  distinctly  visible  to  creatures  on 
his  satellites,  and  cannot  but  afford  reasoning  beings 
on  those  orbs  a  most  astounding  theme  for  study  and 
admiration. 

To  the  inhabitants  of  the  satellites  which  circle 


zoo  OTHER   WORLDS  THAN  OURS. 

round  Saturn,  the  ringed  planet  must  present  an  even 
more  interesting  spectacle.  His  disk,  as  seen  from  the 
nearest  of  his  satellites,  has  a  diameter  of  17  degrees, 
and  an  apparent  surface  exceeding  more  than  nine 
hundred  times  that  of  the  moon.  From  the  farthest 
satellite  his  disk  is  less  than  a  degree  in  diameter,  and 
therefore  not  quite  four  times  as  large  as  our  moon's. 
Between  these  limits  the  apparent  size  of  Saturn  va- 
ries as  we  pass  from  satellite  to  satellite ;  but  from  the 
sixth  satellite  his  apparent  surface  is  twenty-five 
times,  while  from  the  seventh  it  is  sixteen  times  as 
large  as  the  moon's ;  so  that  the  outer  satellite  is  quite 
exceptionally  circumstanced  in  this  respect. 

It  is  not  so  much  from  the  apparent  size  of  his 
disk,  however  (though  in  the  case  of  all  the  inner 
satellites  that  must  be  a  most  remarkable  relation),  as 
from  the  peculiar  character  of  his  ring-system,  that 
Saturn  must  derive  his  chief  interest.  It  is  true  that 
the  inner  satellites  travel  nearly  in  the  plane  of  the 
rings,  so  as  always  to  see  them  nearly  edgewise.  But, 
even  so  viewed,  the  rings  must  present  a  most  striking 
appearance.  From  the  inner  satellite,  indeed,  the  ex- 
treme span  of  the  ring-system  must  be  more  than  90 
degrees ;  *  so  that  when  one  extremity  is  seen  on  the 
horizon  the  system  would  appear  as  an  arch  thickest 
in  the  middle,  extending  over  an  arc  of  about  93  de- 
grees, and  having  the  disk  of  Saturn  at  its  centre. 
When  the  whole  of  this  arch  is  illuminated,  Saturn  is 
"  full ; "  at  other  times  he  presents  all  the  phases 

*  About  93°  according  to  the  best  estimates  of  the  dimensions  of 
the  rings  and  the  distance  of  the  satellite. 


THE  MOON  AND   OTHER  SATELLITES.         2oi 

shown  by  our  moon,  and  the  arch  of  light  is  corre- 
spondingly shortened.  Saturn  "  full  "  and  in  the  ze- 
nith, with  the  ring-system  dependent  on  either  side  of 
his  disk,  must  be  a  glorious  spectacle  as  seen  from  cer- 
tain regions  of  his  innermost  satellite.  The  display 
would  diminish  in  grandeur,  though  not  perhaps  in 
interest,  as  seen  from  satellites  farther  and  farther 
away.  But  the  inhabitants  of  the  outermost  satellite 
of  all  have  the  privilege  of  seeing  the  Saturnian  ring- 
system  opened  out  much  more  fully  than  as  seen  from 
the  other  satellites,  since  the  path  of  this  moon  is  in- 
clined some  15  degrees  to  the  plane  of  the  ring. 

Of  the  satellites  of  Uranus  and  Neptune  little  can 
be  said,  because  so  little  is  known  either  respecting 
these  orbs  themselves  or  their  primaries.  I  may  re- 
mark that,  despite  the  evidence  brought  forward  to 
the  contrary,  I  have  very  little  doubt  that  Uranus  has 
at  least  eight  satellites.  Four  of  those  discovered  by 
Sir  "W.  Herschel  have  not  indeed  been  yet  identified  ; 
but  one  cannot  read  the  account  of  his  method  of  pro- 
cedure without  feeling  that  no  amount  of  mere  nega- 
tive evidence  can  be  opposed  effectively  to  the  posi- 
tive information  he  has  left  respecting  these  four  orbs. 
Indeed,  when  we  remember  that  Uranus  is  twice  as 
far  from  us  as  Saturn,  while  it  has  only  been  in  recent 
times  that  the  eighth  Saturnian  satellite  (the  seventh 
in  position)  has  been  discovered,  we  cannot  but  con- 
sider that  in  all  probability  many  more  Uranian  satel- 
lites will  one  day  be  discovered.  Neptune  also,  no 
doubt,  has  a  large  family  of  satellites  circling  around 
him. 


CHAPTEE  IX. 

METEOE8    AND   COMETS!    THEIR   OFFICE   m   THE   SOLAS 
SYSTEM. 

THEUE  are  few  more  interesting  chapters  in  the 
history  of  astronomy  than  that  which  deals  with  the 
gradual  introduction  of  meteors  into  an  important 
position  in  the  economy  of  the  solar  system.  Eegarded 
for  a  long  time  as  simply  atmospheric  phenomena 
(though  many  ancient  philosophers  held  another  opin- 
ion), it  has  only  been  after  a  long  and  persistent  se- 
ries of  researches  that  they  have  come  at  length  to  be 
regarded  in  their  true  light.  But,  though  the  history 
of  those  researches  is  not  only  full  of  interest,  but 
highly  instructive  and  encouraging,  this  is  not  the 
place  for  entering  at  length  into  its  details.  I  must 
present  facts  and  conclusions,  rather  than  the  narra- 
tive of  observations  or  calculations  by  which  those 
facts  and  conclusions  have  been  established.  Nay,  it 
would  seem  at  first  sight  as  though  even  the  nature 
of  meteors  could  have-  very  little  to  do  with  the  subject 
of  this  treatise,  since  we  cannot  suppose  these  small 
bodies  to  be  inhabited  worlds.  It  will  be  found,  how- 
ever, that,  though  this  is  certainly  true,  there  are 


METEORS  AND   COMETS.  203 

reasons  for  believing  that  meteors  are  associated  in  a 
very  intimate  manner  with  the  general  relations  of 
the  scheme  of  worlds  forming  the  solar  system. 

Under  the  head  "  Meteors  "  I  include  all  those  ob- 
jects which  reach  the  earth's  atmosphere  from  with- 
out, whether  they  actually  make  their  way  to  her  sur- 
face unbroken,  like  the  aerolites ;  or  explode  into 
small  fragments,  as  bolides  and  fire  balls  have  been  ob- 
served to  do ;  or  are  apparently  consumed  in  travers- 
ing the  upper  regions  of  the  air,  as  happens  with  shoot- 
ing or  falling  stars.  All  these  objects,  we  now  know, 
represent  in  reality  bodies  of  greater  or  less  size, 
which,  before  their  encounter  with  the  earth,  were  trav- 
elling around  the  sun  in  orbits  of  greater  or  less  eccen- 
tricity. The  larger  masses,  though  they- must  be  very 
numerous  (or  our  earth  would  not  once  in  many  ages 
encounter  any  of  them),  are  yet  relatively  few  in 
number  as  compared  with  fire-balls,  and  still  more  so 
in  comparison  with  shooting- stars.  It  has  been  calcu- 
lated, indeed,  that  these  last  are  so  numerous  that  the 
earth,  in  passing  through  a  region  of  space  equal  to 
her  own  dimensions,  must  encounter  no  less  than 
thirteen  thousand  of  them ;  while  of  yet  smaller  bod- 
ies, whose  passage  through  our  air  would  only  be  rec- 
ognizable by  telescopic  aid,  she  is  supposed  to  en- 
counter as  many  as  forty  thousand  within  a  similar 
space.  Without  laying  great  stress  on  these  calcula- 
tions, we  may  yet  feel  quite  sure  that  the  earth  must 
encounter  enormous  numbers  of  these  bodies,  from 
the  mere  fact  that,  though  at  any  fixed  station  but  a 
minute  slice  (so  to  speak)  of  the  earth's  atmosphere  is 


Z04  OTHER   WORLDS  THAN  OURS. 

within  view,  and  even  but  a  portion  only  of  that  slice 
visible  to  a  single  observer,  six  or  seven  falling  stars  on 
the  average  may  be  seen  during  each  hour  of  the  night. 

It  will  be  seen,  then,  that  a  problem  of  the  utmost 
importance  was  involved  in  the  question  whether  these 
bodies  came  from  the  interplanetary  spaces,  or  from 
the  region  of  space  over  which  the  earth's  own  attrac- 
tive energies  prevail.  Now  that  we  know  the  former 
view  to  be  the  true  one,  we  recognize  the  fact  that, 
though  each  meteor  may  be  individually  insignificant, 
the  meteors  of  the  solar  system,  looked  on  as  a  single 
family,  form  a  highly-interesting  and  important  portion 
of  the  solar  system. 

But  now  a  yet  more  significant  relation  has  to  be 
considered.  Regarding  meteors  as  planetary  bodies, 
they  might  yet  be  relatively  unimportant,  if  we  had 
any  reason  to  believe  that  they  form  a  sort  of  zone  or 
belt  near  the  earth's  orbit,  resembling  in  a  sense  the 
asteroidal  zone,  only  composed  of  far  smaller  constitu- 
ent bodies.  We  could  not  then  argue,  from  the  number 
of  meteors  encountered  in  a  given  time  by  the  earth, 
the  largeness  of  the  total  number  of  these  bodies ;  for  it 
might  well  be  that  this  zone  had  no  counterpart,  either 
in  the  outer  part  of  the  planetary  system  or  within 
the  orbit  of  the  earth.  What  has  actually  been  dis- 
covered, however,  respecting  the  paths  along  which  the 
meteoric  bodies  have  reached  the  earth,  immensely  en- 
hances the  importance  of  these  objects. 

It  has  been  proved,  on  evidence  perfectly  incontes- 
table, that  two  well-marked  meteoric  systems  travel  in 
orbits  of  enormous  eccentricity.  The  August  meteors 


METEORS  AND   COMETS. 


205 


travel  on  a  path  so  eccentric  that  in  the  neighborhood 
of  the  earth's  orbit  it  may  be  regarded  as  almost  para- 
bolic in  figure.  That  it  is  not  absolutely  parabolic  ia 
shown,  of  course,  by  the  fact  that  a  period  has  been 
assigned  to  the  revolution  of  the  members  of  the  zone. 
No  observations  have  been  indeed  made  by  which  as- 
tronomers could  determine  the  orbit  of  these  meteors, 
since  for  this  purpose  an  exact  determination  of  the 
velocity  with  which  they  enter  the  earth's  atmosphere 
would  be  requisite,  while  the  observations  actually 
made  to  determine  their  velocity  are  confessedly  in- 
exact. But  an  association,  altogether  too  close  to  be 
regarded  as  accidental,  has  been  discovered  between 
their  orbit  and  that  of  a  bright  comet  which  appeared 
in  1862,  and  this,  combined  with  what  has  since  been 
established  respecting  the  relations  between  comets  and 
meteors,  enables  astronomers  to  adopt  quite  confident- 
ly the  orbit  of  the  comet  as  that  of  the  meteoric  system. 
Now,  a  period  of  one  hundred  and  forty -five  years  im- 
plies, according  to  Kepler's  law,  an  orbit  having  a  mean 
distance  nearly  equal  to  that  of  Neptune.  And  since 
the  orbit  is  so  eccentric  as  to  bring  these  bodies  close 
by  the  earth  when  they  are  near  perihelion,  it  follows 
that  their  aphelion  distance  must  exceed  their  mean  dis- 
tance in  the  same  degree.  Hence  the  aphelion  point 
of  the  August  meteors  must  lie  nearly  twice  as  far  away 
from  us  as  the  orbit  of  Neptune. 

The  November  meteors  have  been  shown  in  like 
manner  to  travel  in  a  period  of  thirty-three  and  a  quarter 
years  around  the  sun,  the  aphelion  of  their  orbit  lying 
far  beyond  the  path  of  Uranus. 


Z06  OTHER   WORLDS  THAN  OURS. 

So  far,  then,  as  we  can  judge  from  the  only  two 
meteoric  systems  whose  orbits  can  be  said  to  have 
been  satisfactorily  determined  (though  there  are  many 
other  systems  which  have  been  associated  with  known 
comets),  we  are  led  to  the  conclusion  that  the  meteoric 
orbits  are  for  the  most  part  eccentric.  We  know, 
further,  that  they  are  inclined  in  all  directions  to  the 
plane  in  which  the  earth  travels,  because  we  see  that 
their  constituent  bodies  fall  upon  the  earth  in  direc- 
tions which  show  no  tendency  to  near  coincidence 
with  the  ecliptic. 

Now,  these  two  circumstances  are  full  of  meaning. 
If  the  meteors  travelled  in  nearly  circular  orbits,  at  a 
mean  distance  nearly  equal  to  the  earth's  mean  dis- 
tance from  the  sun,  then  the  earth  would  be  certain  to 
encounter  meteors  in  the  course  of  her  orbital  motion 
round  the  sun.  Again,  if  the  meteors  travelled  in  ec- 
centric orbits,  whose  perihelia  lay  within  the  earth's 
orbit,  and  if  these  orbits  all  lay  in  or  near  the  plane  of 
the  earth's  path,  the  earth  could  not  fail  to  encounter 
meteors  as  she  travelled  round  the  sun.  But  under 
the  actual  circumstances — the  mean  distances  of  the 
meteoric  orbits  being  in  no  way  associated  with  the 
earth's  mean  distance,  and  the  inclination  of  these  or- 
bits to  the  ecliptic  not  being  in  any  way  limited — the 
two  questions  are  at  once  suggested :  1.  "What  is  the 
a  priori  chance  that  the  earth  would  encounter  the 
members  of  any  meteoric  system  taken  at  random? 
and,  2.  If  this  chance  be  small,  what  is  the  conclu- 
sion to  be  drawn  from  the  fact  that  the  earth  encoun- 
ters meteors  belonging  to  many  systems  ? — the  num- 


METEORS  AND   COMETS. 


207 


ber  already  recognized  being  nearly  sixty.  Now, 
assigning  elements  at  random  to  a  meteor-system,  we 
see  that,  unless  the  resulting  orbit  actually  coincides 
with  the  plane  of  the  ecliptic  (a  relation  which  would 
not  happen  in  a  million  trials),  the  orbit  will  intersect 
that  plane  in  two  points,  lying  on  a  straight  line 
through  the  sun.  And,  for  the  earth  to  encounter 
members  of  the  meteoric  system,  it  is  requisite  that 
one  or  other  of  these  two  points  shall  lie  close  to  the 
earth's  orbit.  But  these  points  may  have  any  position 
whatever  in  the  plane  of  the  ecliptic,  and  the  chance 
that  one  of  them  has  the  requisite  position  may  be  re- 
garded as  indefinitely  small.  It  follows,  then,  that 
the  a  priori  chance  of  the  earth's  encountering  the 
members  of  a  meteoric  system  is  indefinitely  small ; 
and  hence  we  conclude  that  the  number  of  meteoric 
systems  she  passes  wholly  clear  of  is  indefinitely  great, 
in  comparison  with  the  number  whose  members  she 
encounters.  But  she  actually  encounters  meteors  be- 
longing to  no  less  than  fifty-six  systems:  hence  the 
total  number  of  meteoric  systems  belonging  to  the 
planetary  scheme  must  be  an  indefinitely  large  multi- 
ple of  the  number  fifty-six,  or,  in  other  words,  it  must 
be  enormously  beyond  our  powers  of  conception. 

But  this  being  so,  it  behooves  us  to  inquire,  first  of 
all,  what  extent  we  must  assign  to  individual  meteoric 
systems,  and  how  densely  we  may  suppose  meteoric 
masses  to  be  strewn  along  each  system ;  and,  secondly, 
what  may  be  the  nature,  quality,  and  substance  of 
these  meteoric  masses.  For  we  clearly  begin  to  see 
that  we  are  in  the  presence  of  relations  which  may — 


zo8  OTHER  WORLDS  THAN  OURS. 

or,  I  should  rather  say,  which  must — affect  most  im- 
portantly the  economy  of  the  solar  system. 

Now,  we  have  seen  something  already  of  the  lon- 
gitudinal extent  of  meteoric  systems,  since  that  extent 
corresponds  to  the  circumference  of  meteoric  orbits, 
and  we  have  seen  that  these  orbits  have  enormous 
dimensions.  We  may,  indeed,  suppose  that  in  some 
cases  the  whole  extent  of  an  orbit  is  not  occupied  by 
meteoric  masses  at  any  one  instant ;  but  even  when, 
as  in  the  case  of  the  November  meteors,  the  annual 
displays  wax  and  wane  in  splendor,  there  is  no  abso- 
lute cessation  in  the  occurrence  of  star-falls  on  the 
date  corresponding  to  such  a  system.  And  taking  full 
account  even  of  the  marked  diminution  which  acta- 
ally  occurs,  we  are  yet  compelled  to  assign  an  enor- 
mous longitudinal  extent  to  that  portion  of  the  system 
which  has  been  poetically  termed  "  the  gem  of  the 
meteor-ring."  For  example,  in  the  November  meteor- 
system,  this  portion  of  the  ring  cannot  be  less  than 
1,000,000,000  of  miles  in  length.  As  to  the  width  of  a 
meteor-system — that  is,  its  extent  in  a  direction  meas- 
ured in  the  plane  of  its  orbit — we  have  no  satisfactory 
information,  because  a  meteor-system  may  extend 
enormously  on  either  side  of  the  point  through  which 
the  earth's  orbit  intersects  it,  and  yet  no  trace  of  that 
extension  be  recognized  by  observers  on  the  earth. 
Still  we  may  conclude  that  this  dimension  lies  in  ex- 
tent somewhere  between  the  longitudinal  extension  of 
the  system  and  the  depth  of  the  meteor-zone — that  is, 
the  length  of  a  line  taken  through  its  square  to  the 
plane  in  which  it  lies.  Now,. of  this  last  dimension  we 


METEORS  AND   COMETS. 


209 


can  form  a  tolerably  accurate  estimate  in  many  in 
stances.  We  know  that  so  long  as  meteors  belonging 
to  any  system  are  flashing  into  view,  our  earth  is  still 
plunging  through  the  system ;  and  if  we  know  the  po- 
sition of  the  system  we  can  determine  its  depth  in 
this  way,  just  as  we  could  determine  the  breadth  of  a 
range  of  hills  if  we  noticed  how  long  a  train,  travelling 
with  known  velocity,  took  in  passing  through  a  tunnel 
which  traversed  the  range  of  hills  in  a  known  direction. 
Judged  in  this  way,  the  depth  of  the  November  meteor- 
zone  would  seem  to  be  one  hundred  thousand  miles  in 
the  part  traversed  by  the  earth  in  1866,  about  sixty 
thousand  miles  in  the  part  traversed  in  1867,  and  con- 
siderably greater  (though  the  zone  was  more  sparsely 
strewn  with  meteors)  where  the  earth  crossed  the  sys- 
tem in  1868  and  1869. 

Now,  as  regards  the  density  with  which  meteors 
are  strewn  in  any  known  system,  I  must  remark  on  a 
mistake  which  has  been  very  commonly  made.  It  has 
been  thought  necessary  to  consider  the  velocity  with 
which  the  meteors  themselves  travel  as  well  as  the 
earth's  velocity,  in  order  to  determine,  from  the  aver- 
age interval  of  time  separating  the  appearance  of 
successive  meteors,  the  average  distance  separating 
neighboring  meteors  from  each  other.  This,  however, 
is  an  erroneous  mode  of  dealing  with  the  problem. 
We  need  only  consider  the  earth's  velocity,  since  the 
meteoric  motions  cannot  possibly  tend  to  increase  the 
total  number  of  encounters.*  Let  us  apply  this  con- 

*  Obviously  the  total  number  of  meteors  encountered  during  the 
earth's  passage  through  a  meteor-stream  will  be  the  number  contained 


210  OTHER    WORLDS  THAN  OURS. 

sideration  to  enable  us  to  form  a  rough  estimate  of 
the  number  of  bodies  in  the  richer  part  of  the  Novem- 
ber meteor-system.  "We  may  fairly  assume  that,  tak- 
ing the  average  of  the  four  displays  of  the  years  1866- 
'69,  the  earth  encountered  more  than  one  meteor  per 
minute  as  she  swept  successively  through  the  system  ; 
or,  conveniently  for  our  purpose,  that  an  average 
distance  of  1,000  miles  separates  meteor  from  me- 
teor throughout  the  "gem  of  the  ring."  Now,  the 
length  of  the  great  cluster  is  at  least  1,000,000,000 
miles,  its  thickness  may  be  fairly  assumed  as  aver- 
aging 100,000  miles,  and  its  width  can  hardly  be  less 
than  ten  times  its  thickness,  since  the  forces  acting 
on  the  system  tend  much  more  largely  to  affect  its 
width  than  its  thickness.  Thus,  with  the  assumed 
average  of  distance  (1,000  miles),  we  find  that  the 
cluster  cannot  contain  less  than  (1,000,000  x  100  x 
1,000)  or  one  hundred  thousand  million  members. 

Mr.  Alexander  Herschel,  from  observations  of  the 
amount  of  light  given  out  by  these  bodies,  and  a  cal- 
culation founded  on  the  velocity  with  which  they  pen- 
etrate our  atmosphere,  has  come  to  the  conclusion 
that  they  must,  for  the  most  part,  be  very  small,  rarely, 
perhaps,  exceeding  a  few  ounces  in  weight.  We  shall 
certainly  not  exaggerate  their  weight  if  we  assign  one- 
hundredth  part  of  an  ounce  to  each.  We  thus  obtain 
for  the  weight  of  the  whole  cluster  one  thousand  mill- 
in  a  cylindrical  space  having  a  cross-section  equal  to  the  earth's,  and 
traversing  the  meteor-stream  from  side  to  side.  The  motion  of  the 
meteors  will  affect  the  particular  set  of  meteors  actually  found  within 
this  space  as  the  earth  traverses  it,  but  will  not  affect  their  number, 
assuming  a  general  uniformity  of  meteoric  distribution. 


METEORS  AND   COMETS.  211 

ions  of  ounces,  or  about  twenty-eight  thousand  tons. 
The  actual  weight  of  the  November  meteor-system 
cannot,  however,  but  enormously  exceed  this  amount ; 
and  therefore  we  recognize  how  erroneous  that  opinion 
is  which  an  eminent  astronomer  recently,  expressed,, 
who  asserted  that  the  united  weight  of  all  the  bodies 
other  than  planets  in  the  solar  system  must  be  esti- 
mated rather  by  pounds  than  by  tons.  We  have  cer- 
tainly no  reason  for  thinking  that  the  November  sys- 
tem, though  one  of  the  most  important  encountered  by 
the  earth,  is  exceptionally  important  in  the  solar  sys- 
tem. On  the  contrary,  we  have  every  reason  the  laws 
of  probability  can  afford  us,  for  believing  that  there 
must  be  millions  of  systems  equally  or  more  extensive. 
And,  further,  the  fall  of  enormous  masses,  many  tons 
sometimes  in  weight,  upon  the  earth,  would  point  to 
the  conclusion  that  the  members  of  the  November 
system  are  exceptionally  insignificant  as  regards  their 
individual  dimensions.  So  that  we  seem  forced  to  the 
conclusion  that  the  aggregate  weight  of  the  various 
meteoric  systems  circulating  around  the  sun  must  be 
estimated  by  billions  of  tons  rather  than  by  any  of  our 
ordinary  units. 

I  have  already  referred  to  the  relation  which  has 
been  detected  between  comets  and  meteor-systems.  Bi- 
zarre as  the  relation  appears,  it  has  been  established  on 
evidence  which  cannot  reasonably  be  disputed.  It  car- 
ries with  it  results  of  extreme  interest  and  importance. 

I  do  not  propose  here  to  enter  into  any  considera 
tion  of  those  enormously  difficult  questions  which  are 
suggested  by  the  study  of  cometic  phenomena.  That 


H2  OTHER    WORLDS  THAN  OURS. 

they  will  before  very  long  receive  their  solution  I 
confidently  believe ;  but  in  the  present  state  of  our 
knowledge  it  would  indeed  be  hazardous  to  speculate 
as  to  what  that  solution  may  be.  I  may  remark  in 
.passing,  that,  while  I  recognize  in  Dr.  Tyndall's  re- 
cently-promulgated theory  on  the  subject  the  indica- 
tion of  a  highly-suggestive  and  promising  line  of 
research,  I  cannot  but  feel  that  cometic  phenomena 
are  far  too  complicated  to  be  directly  accounted  for  in 
the  way  pointed  out  by  that  distinguished  physicist. 
Some  of  the  more  obvious,  and,  I  may  add,  the  more 
generally  known  phenomena,  do  indeed  appear  to  re- 
ceive a  solution  when  examined  under  the  light  of  Dr. 
Tyndall's  researches,  but  numbers  of  others  remain 
not  only  unaccounted  for,  but  standing  apparently  al- 
together opposed  to  his  theory.* 

But  for  my  present  purpose  the  facts  to  be  princi- 
pally noticed  are  in  a  sense  independent  of  any  theory 
which  may  be  formed  respecting  the  nature  of  comets. 
"We  know  that  the  dimensions  of  these  objects  are  in 
many  cases  enormous.  We  know,  further,  that  there 
must  be  many  thousands  of  comets  remaining  undis- 
covered for  each  that  our  astronomers  have  detected. 
And,  lastly,  we  are  led  to  recognize  the  observed 
association  between  certain  meteor-systems  and  cer- 
tain comets  as  indicative  of  a  general  law  by  which,  in 
some  way  as  yet  unexplained,  comets  and  meteors  are 

*  The  theory  recently  put  forward  by  Prof.  Tait  is  altogether  incon- 
sistent with  the  history  of  many  comets.  Indeed,  I  have  been  unable 
to  find  a  single  comet  whose  recorded  changes  of  appearance  counte- 
nance Prof.  Tail's  views. 


METEORS  AND   COMETS. 


213 


associated  together.  Thus,  independently  of  the  con- 
siderations already  adduced,  we  are  led  to  the  conclu- 
sion that  meteor-systems  must  be  very  numerous; 
while  from  the  fact  that  a  meteor-system  so  important 
as  the  November  stream  is  associated  with  a  comet  so 
insignificant  as  Tempel's,  we  conclude  that  those  mag- 
nificent comets  which  have  blazed  in  our  skies — a 
source  at  once  of  wonder  and  perplexity  to  the  astron- 
omer— must  be  associated  with  systems  of  bodies  incal- 
culably more  important  than  the  meteor-system  which 
has  so  often  filled  the  heavens  with  falling  stars. 

]STow,  combining  all  these  results,  we  seem  fairly 
led  to  the  conclusion  that  purposes  of  the  utmost  im- 
portance  in  the  economy  of  the  solar  system  must  be 
subserved  by  these  uncounted  thousands  of  meteoric 
streams.  If,  indeed,  we  could  suppose  that  the  planets 
steered  clear  of  them,  and  that  the  bodies  composing 
them  simply  circulated  unceasingly  in  their  orbits, 
we  might  form  another  opinion.  But  we  know  that 
meteors  are  continually  falling  upon  the  atmosphere 
of  our  own  earth,  either  there  to  be  dissipated  into 
finest  dust  or  to  pass  onward,  with  or  without  explo- 
sion, to  the  actual  surface  of  the  earth ;  and  we  cannot 
doubt  that  in  a  similar  way  countless  thousands  of 
meteors  are  falling,  not  only  upon  all  the  primary 
members  of  the  solar  system,  but  upon  asteroids  and 
satellites — nay,  are  even  streaming  in  among  the  mi- 
nute bodies  composing  the  rings  of  Saturn.  These 
encounters  cannot  be  wholly  without  result,  and  it  is 
quite  conceivable  that  most  injurious  consequences 
might  ensue  to  the  inhabitants  of  all  the  worlds  in  the 


214  OTHER   WORLDS  THAN  OURS. 

Bolar  system  if  the  continual  supply  of  meteoric  matter 
were  importantly  diminished. 

Now,  if  meteoric  masses  fall  continually  upon  the 
planets,  such  masses  must  fall  in  numbers  inconceiv- 
ably greater  upon  the  sun ;  and  it  is  here,  unless  I  mis- 
take, that  the  great  purpose  of  the  meteoric  systems 
becomes  apparent. 

Let  us  clearly  recognize,  however,  why  and  how 
the  sun  must  be  assaulted  by  a  continual  inrush  of 
meteoric  bodies.  We  have  seen  how  enormous  must 
be  the  number  of  these  bodies ;  we  know  how  swiftly 
they  travel,  and  on  what  eccentric  orbits ;  but  we 
must  go  farther  before  we  can  prove  that  they  fall 
upon  the  sun.  For  example,  the  November  meteors 
are  enormous  in  number,  and  travel  with  enormous 
velocity  in  a  very  eccentric  orbit,  but  they  do  not  ap- 
proach the  sun  within  a  distance  of  nearly  ninety  mill- 
ions of  miles.  Nor,  indeed,  can  any  known  meteoric 
system  pour  a  steady  hail  of  meteors,  so  to  speak,  upon 
the  sun  ;  for  he  is  the  ruling  centre  of  every  meteoric 
system,  and  therefore  under  ordinary  circumstances 
the  meteoric  orbits  must  pass  around  him,  and  not  in 
such  a  direction  as  to  intersect  his  substance. 

But  it  is  to  be  remembered  that  meteors  must  be 
infinitely  more  crowded  in  the  neighborhood  of  the 
sun  than  at  a  distance  from  him.  An  indefinitely 
large  number  of  meteoric  orbits  must  absolutely  in- 
tersect in  the  immediate  neighborhood  of  the  sun ; 
and  collisions  must  continually  be  taking  place  as 
countless  thousands  of  meteoric  flights  rush  toward 
and  past  and  then  away  from  their  perihelia.  Where 


METEORS  AND   COMETS.  2l$ 

these  perihelia  lie  close  to  the  sun,  the  velocity  with 
which  the  meteors  travel  must  exceed  two  hundred 
miles  per  second,  and  therefore  the  collision  even  of 
two  minute  meteors  must  result  in  the  generation  of 
an  enormous  amount  of  light  and  heat.  But  that  is 
not  all.  Among  the  collisions  thus  continually  taking 
place  in  the  sun's  neighborhood  there  must  be  a  con- 
siderable proportion  in  which  the  two  bodies  are 
brought  momentarily  almost  to  rest  by  the  shock.  In 
such  cases  the  combined  mass  of  the  two  meteors 
would  fall  directly  upon  the  sun,  a  fresh  supply  of 
light  and  heat  being  generated  as  they  were  brought 
again  to  rest  upon  his  surface. 

Whether  in  the  continual  collisions  of  meteors 
among  themselves,  and  in  their  precipitation  upon  the 
sun's  surface,  we  have  a  sufficient  explanation  of  the 
seemingly  exhaustless  emission  of  light  and  heat  from 
the  sun,  I  should  not  care  positively  to  assert.  Prof. 
Thompson,  who  was  one  of  the  first  to  adopt  this 
view,  has,  I  believe,  abandoned  it ;  though  it  is  wor- 
thy of  remark  that  the  strongest  evidence  in  its 
favor  has  been  obtained  since  he  withdrew  his  sup- 
port from  it,  or  at  least  admitted  that  the  downfall 
of  meteors  on  the  sun's  surface  is  not  alone  sufficient 
to  account  for  the  solar  light  and  heat.  But  I  am 
quite  certain  that  there  is  no  flaw  in  the  evidence  I 
have  adduced  from  the  laws  of  probability  ;  and  that 
we  are  bound  to  accept,  as  a  legitimate  conclusion 
from  that  evidence,  the  theory  that  at  least  an  impor- 
tant proportion  of  the  sun's  heat  is  supplied  from  the 
meteoric  streams  which  circulate  in  countless  millions 


216  OTHER   WORLDS  THAN  OURS. 

around  him.  I  believe  that,  without  adopting  any 
unreasonable  assumptions,  it  might  readily  be  shown 
that  the  whole  even  of  that  enormous  supply  of  light 
and  heat  which  the  sun  emits  on  every  side  is  derived 
from  the  meteoric  streams  belonging  to  the  solar  sys- 
tem or  drawn  in  from  surrounding  space,  as  the  sun, 
attended  by  his  family  of  planets,  sweeps  onward  amid 
the  stellar  groups. 

If  this  view  be  correct,  then  the  meteor-systems 
constitute,  indeed,  a  most  important  part  of  the  sun's 
domain.  They  may  be  said  almost  to  share  with  the 
sun  a  title  to  be  regarded  as  the  source  of  all  the  forms 
of  force  which  exist  throughout  the  solar  system.  It, 
in  the  energies  of  living  creatures  on  earth,  in  the 
forces  derived  from  the  fuel  that  propels  our  engines, 
or  in  the  power  of  winds  and  storms,  we  trace  the 
action  of  the  ruling  centre  of  the  solar  system,  we  may 
trace  back  the  chain  of  causation  yet  one  link  farther, 
and  see  in  the  sun's  emission  of  light  and  heat  the 
result  of  forces  inherent  in  the  meteoric  systems  which 
circle  around  him. 

But  we  must  not  forget  one  most  important  con- 
sideration, which  makes  the  sun  (as  might  be  antici- 
pated) again  the  chief  source  of  all  the  forms  of  force 
existing  within  his  system.  The  motions  of  the  me- 
teoric masses  are  almost  wholly  due  to  the  sun's 
attraction;  and  therefore,  in  so  far  as  those  motions 
are  to  be  regarded  as  a  means  of  renewing  the  solar 
heat,  we  must  regard  the  sun's  attractive  energy  as 
the  source  whence  his  heat  and  all  the  other  forms  of 
force  which  he  exerts  are  in  reality  derived. 


METEORS  AND   COMETS.  217 

Yet  one  step  farther.  The  sun's  attractive  energies 
might  be  increased  a  thousand-fold,  and  yet  not  avail 
to  supply  the  various  forms  of  force  which  are  required 
by  his  dependent  worlds,  were  there  no  external  ma- 
terial on  which  those  energies  could  act  in  such  sort 
as  to  lead  to  the  continual  inrush  of  matter  upon  the 
solar  surface.  Nor  would  it  suffice  if  such  materials, 
even  in  enormous  quantities,  existed  dose  to  the  sun. 
It  is  the  distance  from  which  that  material  is  dragged 
toward  the  sun  which  gives  that  orb  the  power  of 
imparting  those  tremendous  velocities  to  which  the 
collisions  of  the  meteoric  bodies  owe  their  real  effec- 
tiveness. We  thus  find  in  distance,  in  the  simple 
element  of  scale,  the  true  source  of  the  various  forms 
of  force  which  are  continually  exerted  throughout  the 
solar  system.  The  sun  surrounded  by  millions  on 
millions  of  meteoric  masses  close  at  hand  would  be 
powerless,  but  placed  as  ruler  over  a  space  far  wider 
than  the  sphere  circled  by  Neptune's  orbit,  amid 
which  space  those  countless  millions  of  meteors  are 
distributed,  he  becomes  forthwith  the  centre  of  a 
thousand  forms  of  force,  gathered  by  him  continually 
from  the  systems  of  meteors  circling  around  him,  and 
distributed  by  him  abundantly  and  without  ceasing  to 
his  dependent  worlds.* 

*  Just  as  this  work  was  about  to  be  placed  in  the  printer's  hands  I 
received  from  Prof.  Kirkwood,  of  America,  one  of  his  valuable  contri- 
butions to  the  history  of  the  solar  system.  In  it  he  points  to  the 
e-ridence  we  have  that  the  sun,  as  he  speeds  onward  through  space, 
passes  through  regions  in  which  cometic  and  meteoric  materials  are  now 
richly,  now  sparsely  strewn,  and  gathers  in  accordingly  new  stores  of 
force  of  greater  or  less  amount.  The  bearing  of  the  views  of  this  acute 
and  soundly-reasoning  astronomer  (the  Kepler  of  our  day),  not  only  or 
10 


2i 8  OTHER    WORLDS  THAN  OURS. 

It  will  not  fail  to  be  noticed  by  the  thoughtful 
reader  that,  adopting  this  view  of  the  relation  in  which 
meteoric  and  cometic  systems  stand  with  respect  to 
the  sun,  it  seems  necessary  that  we  should  regard 
those  planets  which  I  have  endeavored  to  raise  to 
the  dignity  of  secondary  suns,  as  subordinate  centres 
of  attraction,  around  which  countless  thousands  of  me- 
teoric systems  may  be  supposed  to  circle.  Have  we 
any  evidence  pointing  to  such  a  conclusion  ? 

Now,  there  can  be  no  doubt  that  if  Jupiter,  the 
nearest  of  these  secondary  suns,  did  so  act  upon  a 
passing  comet  as  to  compel  that  body  to  circle  in 
future  around  him,  instead  of  pursuing  its  course 
around  the  sun,  we  could  not  in  any  way  become 
conscious  of  the  event  unless  the  comet  were  an  ex- 
ceptionally large  one.  I  conceive,  however,  that  such 
an  event,  though  undoubtedly  possible,*  must  be  so 

the  theories  dealt  with  in  the  above  chapter,  but  on  those  considered  in 
the  chapters  which  follow,  will  be  seen  at  once. 

*  It  is  necessarily  possible  in  the  case  of  any  planet,  but  must  in 
many  cases  be  highly  improbable.  For  example,  astronomers  sometimea 
assert  that  meteoric  masses  passing  near  the  earth  might  become 
satellites  of  hers,  but  in  reality  this  is  a  very  unlikely  event,  because 
the  maximum  velocity  which  a  body  travelling  under  the  earth's  influence 
can  have  (that  is,  the  velocity  acquired  by  a  body  travelling  from  infinity 
to  a  perigee  close  to  the  earth)  is  less  than  the  velocity  with  which  a 
body  circling  on  any  orbit  round  the  sun  would  move  when  at  the 
earth's  distance  from  him,  unless  its  orbit  were  very  eccentric  and  the 
aphelion  close  by  the  earth's  orbit.  Bodies  travelling  from  outer  space 
toward  the  sun  cannot  by  any  possibility  become  satellites  of  the  earth, 
because  they  would  always  have  a  velocity  greater  than  that  which  her 
attraction  can  master.  Even  in  the  rare  event  of  their  grazing  her 
atmosphere,  and  so  losing  a  large  share  of  their  velocity,  they  could  not 
become  permanent  satellites  of  hers,  because,  returning  to  the  scene  of 
encounter,  they  would  lose  yet  a  larger  share  of  their  velocity,  and  so 
must  be  brought,  and  that  soon,  to  her  surface. 


METEORS  AND   COMETS.  21g 

uncommon,  that  the  number  of  cometic  systems  thus 
forced  to  own  Jupiter  as  their  centre  of  attraction 
must  be  relatively  few.  But  in  another  way  the  plan- 
et does  exhibit  his  power  as  a  comet-ruler,  making 
comets  recognize  him  as  a  sort  of  subordinate  master, 
the  sun  being  their  primary  ruler.  "When  comets 
coming  from  outer  space  pass  near  enough  to  Jupiter, 
he  sways  them  so  markedly  from  the  orbit  they  are 
pursuing  that  the  scene  of  encounter  becomes  the 
aphelion  of  their  orbit,  or  nearly  so.  Thence  they 
pass  on  their  new  orbit  to  their  perihelion,  returning 
again  presently  to  the  scene  of  their  encounter  with 
Jupiter,  and  so  revolving  in  an  orbit  having  its 
aphelion  close  by  the  orbit  of  Jupiter,  until  haply  the 
giant  is  again  near  the  scene  of  encounter  at  the  mo- 
ment when  the  comet  comes  back  to  it.  In  this  case 
a  fresh  struggle  takes  place,  the  overmastering  attrac- 
tion of  the  planet  necessarily  prevailing,  and  the  comet 
being  often  dismissed  on  a  new  orbit,  whose  perihelion, 
instead  of  its  aphelion,  lies  close  by  the  orbit  of  Ju- 
piter. 

Now,  we  know  that  such  events  as  these  must  be 
of  frequent  occurrence  as  Jupiter  sweeps  swiftly  round 
on  his  orbit.  For  we  recognize  several  comets  which 
have  evidently  been  compelled  by  Jupiter  to  take  up 
such  orbits  as  I  have  spoken  of — a  family  of  comets, 
in  fact,  including  Encke's,  Faye's,  and  Brorsen's  com- 
ets, Winnecke's  short-period  comet,  and  several  others. 
"We  judge  further,  from  the  laws  of  probability,  that, 
for  each  discovered  comet  of  this  family,  there  must 
be  thousands  which  have  escaped  detection.  So  that 


220  OTHER    WORLDS  THAN  OURS. 

around  the  orbit  of  Jupiter  (if  not  around  Jupiter 
himself)  there  cling  the  aphelia  of  myriads  of  cometic 
orbits,  whose  perihelia  lie  at  all  conceivable  distances 
from  the  sun  less  than  the  distance  of  Jupiter. 

Saturn  also  has  his  family  of  comets ;  so  also  have 
Uranus  and  Neptune.  The  comet  associated  with  the 
November  meteors  belongs  indeed  to  the  Uranian 
comet-family,  and  the  epoch  (126  A.  D.)  has  even  been 
pointed  out  when  this  comet  fell  under  the  dominion 
(subject  always  to  the  sun's  superior  control)  of  that 
distant  planet. 

And  here  I  may  refer  to  a  view  which  1  have  long 
entertained  respecting  the  purposes  which  meteoric 
and  cometic  systems  have  fulfilled  in  the  past  history 
of  the  solar  system.'35'  We  know  that  the  materials 
composing  meteors,  and  we  conclude,  therefore,  that 
those  composing  comets,  do  not  differ  from  those 
which  constitute  the  earth  and  sun,  and  presumably 
the  planets  also.  Therefore,  under  the  continual  rain 
of  meteoric  matter,  it  may  be  said  that  the  earth,  sun, 
and  planets,  are  growing.  Now,  the  idea  obviously 
suggests  itself,  that  the  whole  growth  of  the  solar 
system,  from  its  primal  condition  to  its  present  state, 
may  have  been  due  to  processes  resembling  those 

*  Since  the  present  chapter  was  written,  I  find  that  the  hypothesis 
here  put  forward  has  in  a  general  way  been  touched  on  by  more  than 
one  astronomer  and  physicist.  I  believe,  however,  that  here,  for  the 
first  tune,  it  has  been  associated  with  the  chief  features  of  the  solar 
system.  It  was  suggested  in  note  B  (Appendix)  to  my  treatise  on  Sat- 
urn. But,  as  a  matter  of  fact,  when  that  note  was  written,  as  also  when 
those  passages  were  published  in  which  the  same  hypothesis  is  touched 
by  other  authors,  the  decisive  evidences  hi  favor  of  the  theory  were 
wanting. 


METEORS  AND   COMETS.  22l 

which  we  now  see  taking  place  within  its  bounds.  It 
is  of  course  obvious  that,  if  this  be  so,  the  number 
of  meteoric  and  cometic  systems  must  have  been 
enormously  greater  originally  than  it  is  at  present. 
Countless  millions  of  meteoric  systems,  travelling  in 
orbits  of  every  degree  of  eccentricity  and  inclination, 
travelling  also  in  all  conceivable  directions  around  the 
centre  of  gravity  of  the  whole,  would  go  to  the  making 
up  of  each  individual  planet.  A  marked  tendency  to 
aggregate  around  one  definite  plane,  and  to  move  in 
directions  which,  referred  to  that  plane,  corresponded 
to  the  present  direction  of  planetary  motion,  would 
suffice  to  account  for  the  present  state  of  things.  The 
effect  of  multiplied  collisions  would  necessarily  be  to 
eliminate  orbits  of  exaggerated  eccentricity,  and  to 
form  systems  travelling  nearly  on  the  mean  plane  of 
the  aggregate  motions,  and  with  a  direct  motion. 
Further,  where  collisions  were  most  numerous,  there 
would  be  found  not  only  the  most  circular  resulting 
orbits,  not  only  the  greatest  approach  to  exact  coin- 
cidence of  such  orbits  with  the  mean  plane  of  the 
whole  system,  but  the  bodies  formed  out  of  the  result- 
ing systems  would  there  exhibit  rotations,  coinciding 
most  nearly  with  the  mean  plane  of  the  entire  sys- 
tem.* 

It  seems  to  me  that,  not  only  has  this  general  view 

*  This  conclusion  depends  on  a  well-known  law  of  probability.  It 
may  be  thus  illustrated :  If  we  have  in  a  bag  a  hundred  white  and  a 
hundred  black  balls,  and  take  out  at  random  a  number  of  balls,  then 
the  larger  that  number,  the  more  nearly  (in  all  probability)  will  the 
number  of  black  and  white  balls  included  in  it  approach  to  a  ratio  of 
equality. 


222  OTHER   WORLDS  THAN  OURS. 

of  the  mode  in  which  our  system  has  reached  its  pres- 
ent state  a  greater  support  from  what  is  now  actually 
going  on  than  the  nebular  hypothesis  of  Laplace,  but 
that  it  serves  to  account  in  a  far  more  satisfactory 
manner  for  the  principal  peculiarities  of  the  solar  sys- 
tem. I  might  indeed  go  further,  and  say  that,  where 
these  peculiarities  seem  to  oppose  themselves  to  La- 
place's theory,  they  give  support  to  that  which  I  have 
put  forward. 

For  example,  what  is  there  in  the  nebular  hypothe- 
sis which  affords  even  a  general  explanation  of  the 
strange  varieties  of  size  observed  in  the  planetary  sys- 
tem ?  How  can  that  hypothesis  be  reconciled  with 
the  remarkable  variations  of  inclination  observed 
among  the  planets,  or  with  the  retrograde  and  almost 
perpendicular  motion  of  the  satellites  of  Uranus  ? 
Nor,  again,  is  the  hypothesis  consistent  with  the  ob- 
served peculiarities  of  motion  of  those  meteoric  sys- 
tems which  we  must  now  regard  as  regular  members 
of  the  solar  system. 

Now,  according  to  the  hypothesis  I  have  put  for- 
ward above,  a  general  explanation  of  all  these  matters 
is  at  once  suggested.  Let  us  consider : 

In  the  neighborhood  of  the  great  central  aggre- 
gation which  would  undoubtedly  result  from  the  mo- 
tions of  such  meteoric  systems  as  I  have  considered, 
all  the  motions  would  be  very  rapid.  They  would,  in 
fact,  resemble  the  motions  now  actually  observed  in 
the  sun's  neighborhood.  Here,  therefore,  subordinate 
aggregations  would  form  with  difficulty,  since  they 
would  have  small  power  of  overruling  meteoric  sys- 


METEORS  AND   COMETS. 


223 


terns  rushing  with  so  great  a  velocity  past  them.  In 
the  sun's  immediate  neighborhood,  then,  we  should 
expect  to  find  relatively  small  planets ;  and  we  do  ac- 
cordingly find  that  Mercury,  nearest  to  him,  is  the 
smallest  of  the  planets,  Venus  larger,  and  the  earth 
(yet  farther  away)  not  only  larger  than  Venus,  but 
adorned  with  an  attendant  satellite. 

Now,  at  a  much  greater  distance  from  the  sun  the 
meteoric  motions  would  be  so  much  less,  that  here, 
supposing  only  a  suitable  mean  density  of  aggrega- 
tion, it  would  be  possible  for  subordinate  centres  of 
aggregation  of  far  greater  magnitude  to  form.  These 
centres  would  increase  in  importance  as  they  swept 
round  the  central  aggregation,  continually  gathering 
fresh  recruits.  Indeed,  though,  as  now,  they  would 
not  be  able  to  prevent  the  major  part  of  the  materials 
rushing  from  outer  space  toward  the  sun  from  aggre- 
gating round  him,  they  would  still  gather  in  no  in- 
considerable portion  of  those  materials.  Where  the 
largest  portion  would  be  gathered  would  depend  on 
the  way  in  which  (taking  a  general  view  of  the  sys- 
tem) the  quantity  of  material  increased  toward  the 
neighborhood  of  the  centre.  For  clearly,  while  dis- 
tance from  the  sun  would  increase  the  facility  with 
which  materials  would  be  gathered  in — since  the  sun's 
influence  would  diminish  with  distance,  it  would  also 
affect  the  quantity  of  material  available — since,  from 
a  very  early  period,  the  system  must  have  begun  to 
show  an  appearance  resembling  that  now  presented 
by  the  zodiacal  light,  that  is,  a  general  increase  of 
density  toward  the  centre. 


Z24 


OTHER  WORLDS  THAN  OURS. 


Assuming  that  the  region  of  maximum  aggrega- 
tion was  that  where  the  influence  of  the  ruling  centre 
first  became  so  far  diminished  with  distance  as  to  ren- 
der the  formation  of  a  great  subordinate  aggregation 
possible,  we  should  have  the  innermost  of  the  outer 
series  of  planets  also  the  most  bulky  ;  and  next,  with- 
in that  giant  planet  we  should  find  a  relatively  barren 
space,  cleared  of  material  not  only  by  the  sun's  still 
powerful  influence,  but  also  by  the  influence  of  this 
first  important  subordinate  aggregation.  The  initial 
assumption  is,  in  itself,  at  least  not  improbable,  and, 
having  once  admitted  it,  we  find  an  explanation  of  the 
giant  mass  of  Jupiter,  of  the  comparative  poverty  of 
material  just  within  the  orbit  of  Jupiter,  and  hence,  of 
the  condition  of  the  asteroidal  zone,  and  of  the  small- 
ness  of  the  planet  Mars  next  within  that  zone — though 
this  planet  far  outweighs  (according  to  Leverrier's  es- 
timate) the  united  mass  of  all  the  asteroids.  Beyond 
the  orbit  of  Jupiter,  we  should  expect  (after  passing 
an  enormously  wide  space,  bare  of  worlds)  to  find  still 
a  great  abundance  of  material,  and  an  even  greater 
facility  in  the  aggregation  of  that  material.  Thus  the 
existence  of  the  planet  Saturn,  next  in  importance  to 
Jupiter,  and  surpassing  him  in  the  complexity  of  his 
attendant  system,  is  accounted  for ;  yet  farther  away 
we  look  for  and  find  still  an  abundance  of  material, 
and  that  material  somewhat  more  uniformly  strewn, 
while  the  sun's  small  influence  is  indicated  by  the  ex- 
istence of  satellites,  of  which  doubtless  many  more  will 
one  day  be  discovered  by  astronomers. 

And  as  to  the  rotations  of  the  various  members  of 


METEORS  AND   COMETS.  225 

the  solar  system  we  find  some  account,  necessarily  not 
exact,  given  by  this  theory.  I  have  mentioned  above 
the  results  to  be  looked  for ;  those  observed  are  closely 
accordant  with  that  view.  Thus  the  sun,  the  largest 
member  of  the  system,  and  specially  preeminent  with- 
in its  inner  division,  rotates  on  an  axis  inclined  but 
about  seven  degrees  to  the  mean  plane  of  the  system. 
Mars,  the  least  member  of  this  system,  has  an  inclina- 
tion of  no  less  than  twenty-eight  degrees ;  the  larger 
earth  an  inclination  of  but  twenty-three  degrees.  The 
inclinations  of  Yenus  and  Mercury  are  undetermined ; 
they  may  be  expected  to  be  large,  not  merely  on  ac- 
count of  the  smallness  of  these  bodies,  but  on  account 
of  their  proximity  to  the  sun.  Of  the  outer  division 
of  the  system,  Jupiter,  the  largest,  has  an  inclination 
of  little  more  than  three  degrees  ;  Saturn  has  a  very 
considerable  inclination  (more  than  twenty-six  de- 
grees) ;  Uranus  has  an  inclination  which  may  be  de- 
scribed as  actually  greater  than  ninety  degrees,  since 
he  rotates  backward  with  his  equator  inclined  seventy- 
six  degrees  to  the  ecliptic.  And  lastly,  if  the  obser- 
vations hitherto  made  on  Neptune's  satellites  are  to 
be  trusted,  this  planet,  probably,  rotates  in  a  retrograde 
manner,  his  equator  being  inclined  some  twenty-six 
degrees  to  the  horizon ;  so  that,  to  render  the  compari- 
son between  his  rotation  and  that  of  the  other  mem- 
bers of  the  solar  system  complete,  he  may  be  said  to 
rotate  in  a  direct  manner  with  his  equator  inclined 
some  one  hundred  and  fifty-four  degrees  to  the  ecliptic. 
The  great  inclination  and  eccentricity  of  many  of 
the  asteroidal  orbits  are  also  accounted  for  more  satis- 


t26  OTHER    WORLDS  THAN  OURS. 

factorily  by  this  theory  than  by  the  nebular  hypothe- 
sis. In  fact,  there  is  an  absolute  incorrectness  in  the 
assertion  that  the  smallness  of  the  asteroids  can  (on 
the  ordinary  view  of  their  origin)  explain  the  relatively 
irregular  nature  of  their  motions.  Their  minuteness 
doubtless  brings  them  more  under  the  disturbing  influ- 
ence of  Jupiter  than  a  single  massive  planet  at  the 
same  distance  from  the  sun  would  be.  But  the  attrac- 
tions of  Jupiter  can  have  no  influence  in  causing  the 
asteroids  to  depart  so  widely  as  they  do  from  the  eclip- 
tic, since  his  path  lies  quite  close  to  the  ecliptic,  and 
even  nearer  to  the  mean  plane  of  the  solar  system. 
But  bodies  formed  as  the  asteroids  are  supposed  to  be, 
according  to  the  hypothesis  I  have  suggested,  would  ne- 
cessarily exhibit  a  much  greater  variety  of  motion  than 
would  be  recognized  in  the  case  of  the  larger  planets. 
Another  point  in  which,  as  I  conceive,  my  hypoth- 
esis is  more  satisfactory  than  the  nebular  one,  consists 
in  the  fact  that  it  suggests  an  explanation  of  the  pecu- 
liarities observed  in  the  planetary  periods.  Prof.  Kirk- 
wood's  researches  into  the  various  relations  of  commen- 
Burability  presented  among  the  periods  of  planets  and 
satellites,  and  the  known  effects  of  commensurability 
in  encouraging  the  accumulation  of  planetary  pertur- 
bations, will  at  once  suggest  to  the  mathematical 
reader  the  way  in  which  a  system,  forming  in  such  a 
manner  as  I  have  imagined,  might  be  expected  to  ex- 
hibit the  presence  of  law  as  regards  distances  and  pe- 
riods. I  know  of  nothing  in  the  nebular  hypothesis 
which  encourages  the  belief  that  a  system  framed  as 
Laplace  conceived  the  solar  system  to  be,  would  ex- 


METEORS  AND   COMETS.  227 

hibit  any  such  laws  as  are  found  within  the  planetary 
scheme. 

The  hypothesis  I  have  put  forward  also  gets  rid  of 
that  which  has  always  seemed  to  me  the  great  difficulty 
of  the  nebular  hypothesis.  According  to  the  views  of 
Laplace,  Neptune  must  have  been  formed  millions  of 
ages  before  Uranus,  Uranus  as  long  before  Saturn, 
Saturn  as  long  before  Jupiter,  and  so  on.  Now,  we  know 
that  the  appearance  of  those  primary  members  of  the 
solar  system  which  we  are  best  able  to  study  does  not 
indicate  any  such  enormons  disproportion  in  the  ages 
of  the  planets,  even  if  it  does  not  indicate  that  the  plan- 
ets were  formed  nearly  at  the  same  era.  According  to 
my  hypothesis,  the  various  processes  of  aggregation 
would  go  on  simultaneously  (just  as  the  influences 
which  Jupiter  has  on  comets  are  now  exerted  simulta- 
neously with  those  more  powerful  influences  possessed 
by  the  sun) ;  and  though  the  various  orbs  formed  by 
those  processes  would  not  necessarily  be  completed 
simultaneously,  there  would  be  no  such  enormous  dis- 
proportion in  their  age  as  is  necessary  according  to  the 
theory  of  Laplace. 

Yet  another  strong  point  in  favor  of  this  hypothe- 
sis resides  in  the  circumstance  that  we  now  have  every 
reason  to  believe  that  all  the  planets  are  constituted  of 
the  same  elements.  When  it  was  thought  that  Jupiter 
might  be  a  watery  globe,  for  instance,  there  was  some 
evidence  in  favor  of  Laplace's  theory.  But  we  now 
know  that  Jupiter  is  not  constituted  differently,  in  all 
probability,  from  the  earth  and  sun,  as  according  to 
Laplace's  theory  he  must  have  been.  Since,  then,  we 


228  OTHER   WORLDS   THAN  OURS. 

know  tbat  meteors  contain  the  same  elements  which 
exist  in  the  constitution  of  sun  and  planets,  we  have 
here  a  very  strong  argument  in  favor  of  the  view  that 
they  have  played  the  important  part  I  have  assigned 
to  them  in  the  formation  of  the  solar  system. 

But,  after  all,  the  strongest  evidence  in  favor  of  the 
hypothesis  I  have  suggested,  consists  in  the  fact  that 
the  processes  by  means  of  which  I  conceive  the  solar 
system  to  have  been  formed,  are  undoubtedly  going  on 
before  our  eyes.  There  may  be  little,  indeed,  in  the 
downfall  of  meteoric  showers  to  suggest  the  idea  of 
world-formation  or  sun-formation ;  little  in  the  present 
aspect  of  the  zodiacal  light  or  of  the  solor  corona,  to 
present  to  the  mind's  eye  a  picture  of  that  vaster 
agglomeration  of  meteoric  and  cometic  systems,  all 
speeding  with  inconceivable  velocities  on  their  inter- 
lacing orbits,  which  I  imagine  to  have  been  the  em- 
bryon  of  the  solar  scheme.  But  sun  and  planets  are 
growing,  however  slowly,  as  the  meteoric  hail  falls 
continuously  upon  them ;  the  zodiacal  light  and  the 
solar  corona  are  doubtless  due  to  the  existence  of 
meteoric  systems,  resembling  (however  relatively  in- 
significant) those  which  I  have  pictured  as  the  materi- 
als of  the  planetary  scheme.  In  the  Saturnian  rings, 
also,  which  have  been  proved  by  the  researches  of 
Maxwell  and  others  to  consist  of  multitudes  of  dis- 
crete bodies,  we  have  evidence  of  the  same  sort  in  the 
case  of  a  subordinate  centre  of  aggregation.  So  that 
we  have  a  form  of  evidence  which  was  wanting  in  the 
case  of  the  nebular  hypothesis,  in  favor  of  this  other 
hypothesis,  by  which,  as  in  Laplace's,  the  present  state 


METEORS  AND   COMETS.  229 

of  the  solar  system  is  regarded  as  the  result  of  a  pro- 
cess of  development,  and  not  of  special  creative  fiats 
of  the  Almighty. 

In  this  last  respect,  the  hypothesis  I  have  put  for- 
ward will  doubtless  seem  objectionable  to  those  who 
imagine  that,  in  indicating  processes  according  to 
which  the  solar  system  may  have  reached  its  present 
condition,  astronomers  are  attacking  the  attributes  of 
God.  This  will  be  the  more  unfortunate,  because 
those  who  entertain  this  strange  view  may  be  re- 
garded as  probably  so  far  beyond  the  reach  of  argu- 
ment as  to  be  unlikely  ever  to  abandon  their  objection. 
Otherwise,  it  might  avail  to  point  out  that,  as,  in  all 
that  surrounds  us,  we  find  God  acting  through  second 
causes,  we  can  have  no  reason  for  assigning  limits  to 
the  range  of  space  or  time  within  which  He  so  acts ; 
that  is,  we  can  have  no  reason  for  believing  that  we 
can  point  to  a  time  when  He  acted  directly  upon  the 
universe :  and  further,  that  it  gives  an  altogether  high- 
er idea  of  that  wisdom  which  must,  in  any  case,  be 
far  above  our  conceptions,  to  regard  the  laws  of  God 
as  so  perfect  that  they  operate  always  to  work  out  His 
will — without  the  necessity  of  special  interference  on 
His  part — than  to  see  His  hand  directly  operative  in 
all  the  phenomena  of  the  universe. 


CHAPTEK  X. 

OTHER   SUNS   THAN   OUKS. 

"WE  are  now  to  venture  into  regions  where  we  shall 
no  longer  have  clear  lights  to  guide  us.  Tremendous 
as  are  the  dimensions  of  the  solar  system,  the  widest 
sweep  of  the  planetary  orbits  sinks  into  insignificance 
compared  with  the  distances  which  separate  from  us 
even  the  nearest  of  the  fixed  stars.  From  beyond 
depths  which  the  human  mind  is  utterly  unable  to 
conceive  there  come  to  us  the  rays  of  light  which 
myriads  of  those  orbs  are  pouring  forth,  and  it  is  from 
the  lessons  taught  us  by  these  light-rays  that  we  are 
to  form  our  ideas  concerning  the  nature  of  the  orbs 
which  emit  them.  Very  carefully  and  cautiously  must 
we  proceed,  if  we  would  avoid  being  led  into  vain 
imaginings.  It  will  but  mislead  us  to  pass  a  single 
step  beyond  the  path  which  is  dimly  lighted  for  us, 
and  yet  that  path  is  so  narrow  and  so  obstructed  with 
difficulties,  that  we  find  ourselves  continually  tempted 
to  leave  it,  and  to  venture  forward  on  the  alluring  and 
easy  paths  which  speculation  opens  out  on  every  hand 
around  us. 


OTHER  SUNS  THAN  OURS.  23! 

And  yet  we  may  well  remain  content  to  listen  only 
to  the  teachings  of  known  facts.  Even  so  restraining 
ourselves,  we  have  in  reality  a  wide  and  noble  domain 
to  explore.  Facts  which  seem  severally  unimportant, 
are  found,  when  considered  as  parts  of  a  grand  whole, 
to  indicate  relations  so  impressive  and  so  interesting, 
that  the  revelations  of  the  telescope  within  the  solar 
system  are  apt  to  seem  commonplace  beside  them. 
We  have,  in  fact,  to  consider  no  longer  the  structure 
of  a  system — the  architecture  of  the  universe  is  our 
theme. 

Let  us  examine  carefully  the  evidence  which  sci- 
ence has  gathered  together  for  us,  endeavoring  at  each 
step  to  gain  the  full  amount  of  knowledge  the  several 
facts  involve,  while,  at  the  same  time,  cautiously  refrain- 
ing from  any  attempt  to  overstep  the  bounds  indicated 
by  our  evidence. 

In  the  first  place,  let  us  consider  what  may  be 
learned  from  the  analogy  of  the  solar  system.  The 
study  is  an  inviting  one,  since  the  discoveries  on  which 
we  are  to  found  our  views  have  been  made  so  recently, 
that  the  subject  has  all  the  charnr  of  novelty  and  fresh- 
ness, while  it  involves  the  consideration  of  the  soundest 
and  most  instructive  mode  of  pursuing  our  researches. 

We  have  seen  in  the  solar  system  a  variety  and 
complexity  of  structure,  such  as,  half  a  century  ago, 
few  astronomers  would  have  thought  of  ascribing  to 
it.  When  Sir  William  Herschel  began  that  noble 
series  of  researches  amid  the  sidereal  depths  by  which 
his  name  has  been  rendered  illustrious,  he  saw  in  the 
solar  system  a  scheme  very  different  indeed  from  that 


I3z  OTHER   WORLDS  THAN  OURS. 

which  is  presented  to  our  contemplation.  He  beheld 
a  vast  central  body,  surrounded  by  a  limited  number 
of  orbs,  some  of  which  were  the  centres  of  subordinate 
schemes  of  greater  or  less  extent.  When  we  have 
added  the  ring  of  Saturn  as  the  only  formation  dif- 
fering from  planets  and  satellites  in  character,  and  the 
comets  few  and  far  between,  which  seemed  rather  acci- 
dental tributaries  of  the  sun  than  regular  members  of 
his  family,  we  have  considered  all  the  features  which 
the  solar  system,  as  known  in  Sir  William  Herschel's 
day,  presented  to  the  contemplation  of  astronomers. 

With  us  it  is  very  different.  We  see  that  there 
exists  within  the  solar  system  a  variety  of  size  and 
structure,  of  motion,  arrangement,  and  aggregation, 
which  is  already  inconceivable,  and  yet  doubtless  but 
faintly  shadows  forth  the  real  complexity  and  richness 
of  the  scheme  swayed  by  our  sun.  Perhaps  it  is  in 
considering  the  solar  system  in  the  particular  light  in 
which,  in  this  treatise,  I  have  had  occasion  to  present 
it,  that  this  wonderful  variety  of  conformation  is  made 
most  strikingly  apparent.  But,  apart  from  all  specu- 
lative theories,  there  can  be  no  doubt  that  the  solar 
system  presents  to  us  a  subject  of  study  amazing  in 
itself,  but  most  amazing  when  we  regard  it  as  supply- 
ing the  analogies  which  are  to  guide  us  in  forming  our 
views  respecting  the  sidereal  system.  Besides  the  fam- 
ily of  planets  circling  round  the  sun,  besides  the  sys- 
tem of  dependent  orbs  which  circle  round  the  planets, 
we  see  a  zone  in  which  independent  planets  circle  by 
hundreds,  perhaps  even  by  myriads,  around  the  solar 
orb ;  we  see  the  ring  of  Saturn  composed  of  thousands 


OTHER  SUNS  THAN  OURS.  233 

of  tiny  bodies ;  we  see  the  meteoric  systems  in  count- 
less hosts ;  we  see  the  comets  of  our  scheme  in  mill- 
ions on  millions ;  and  less  certainly,  but  still  not  in- 
distinctly, we  recognize  the  existence  of  a  multitude 
of  new  and  hitherto  unsuspected  forms  of  matter 
within  the  circle  of  our  sun's  attraction. 

What  opinion,  then,  are  we  to  form — even  here,  at 
the  very  outset  of  our  inquiry — respecting  the  sidereal 
scheme  of  which  our  sun  forms  but  a  unit  ?  Surely 
it  would  be  to  lose  sight  of  the  significant  lesson 
taught  us  by  the  solar  system,  it  would  be  to  forget 
how  sure  and  safe  a  guide  the  greatest  of  modern  as- 
tronomers found  in  the  teachings  of  analogy,  to  adopt 
the  same  view  now  which  that  great  astronomer 
adopted  a  century  ago.  If,  viewing  the  solar  system 
as  consisting  of  discrete  orbs,  comparable  one  with 
another  in  size,  and  distributed  not  without  a  certain 
uniformity  around  their  ruling  centre,  Sir  William 
Herschel  held  that  the  sidereal  scheme  presented 
somewhat  similar  relations,  surely  we,  who  know  cer- 
tainly that  the  solar  system  is  constituted  so  differ- 
ently, must  adopt  a  far  different  view  of  the  sidereal 
scheme  also. 

Let  us  remember  that  there  is  here — so  far  as  our 
respect  and  admiration  for  Sir  William  Herschel  are 
concerned — a  choice  between  two  courses.  Assuming, 
as  indeed  is  just,  that  the  views  of  our  great  men  are 
not  rashly  to  be  thrown  on  one  side,  we  have  to  choose 
whether  we  would  rather  abandon  the  views  which  Sir 
William  Herschel  formed  about  facts,  or  the  views 
which  he  formed  about  principles .  If  we  accept  his 


'34 


OTHER    WORLDS  THAN  OURS. 


opinion  (or  rather,  after  all,  his  mere  suggestion)  that 
the  stars  are  tolerably  uniform  in  magnitude  and  dis- 
tribution, we  must  abandon  the  analogy  of  the  solar 
system.  If,  on  the  contrary,  we  accept  Sir  William 
Herschel's  often-expressed  opinion  that,  in  theorizing 
about  the  unknown,  there  can  be  no  safer  guide  than 
the  analogy  of  known  facts,  we  must  abandon  the 
view  (which  seemed  to  him  but  probable)  that  the  stars 
are  distributed  with  tolerable  uniformity  throughout 
our  galaxy,  and  are  comparable  inter  se  in  magnitude 
and  splendor. 

There  can  be  no  doubt  which  course  is  preferable. 
We  know  certainly  that  Sir  William  Herschel  was 
often  mistaken,  as  all  men  must  be,  in  matters  of  fact ; 
while  we  know  with  equal  certainty  that  he  owed  the 
marvellous  success  with  which  he  theorized,  to  his 
adoption  of  the  principle  that  analogy  is  the  chief  and 
the  best  guide  for  the  student  of  astronomy. 

We  are  compelled,  then,  in  our  very  respect  and 
admiration  for  the  greatest  astronomer  of  modern 
times,  to  regard  the  constitution  of  the  sidereal  system 
as,  in  all  probability,  very  different  from  what  he 
imagined. 

We  must  be  prepared  to  expect  an  infinite  variety 
of  figure,  of  structure,  of  motion,  and  of  aggregation 
throughout  the  galactic  scheme.  If  some  orbs  within 
that  scheme  seem  probably  to  be  suns  like  our  own, 
we  must  not  be  surprised  to  find  others  which  are 
probably  far  larger  or  far  smaller.  We  may  look  for 
objects  differing  as  much  from  the  suns  of  the  sidereal 
system  as  the  asteroidal  zone  differs  from  Saturn  or 


OTHER  SUNS  THAN  OURS.  235 

from  Jupiter.  So  that,  if  we  should  recognize  evidence 
of  the  existence  of  clusters  of  minute  stars — a  whole 
cluster,  perhaps,  not  equalling  in  real  importance  the 
least  of  the  suns  of  the  system — we  may  accept  that 
evidence  without  any  scruples  suggested  by  the  im- 
probability of  the  conclusion  to  which  it  points. 
Again,  we  may  expect  to  find  schemes  within  the  si- 
dereal system,  differing  as  much  from  discrete  stars  or 
star-clusters  as  the  rings  of  Saturn  differ  from  the 
primary  planets  or  from  the  asteroidal  zone.  So  that, 
if  we  should  recognize  evidence  of  the  existence  of  rel- 
atively minute  clusters,  whose  components  are  either 
BO  small  or  so  closely  aggregated  as  not  to  be  sepa- 
rately visible  even  in  our  most  powerful  telescopes, 
this  evidence  may  fairly  be  accepted  as  accordant  with 
the  only  analogy  we  have  for  our  guidance.  Yet  once 
more :  we  may  look  for  systems  differing  as  much 
from  all  ordinary  star-clusters  as  the  eccentric  and  far- 
reaching  meteor-systems  differ  from  the  symmetrical 
rings  of  Saturn.  So  that,  if  we  should  find  evidence 
of  strange  schemes  within  the  sidereal  system,  schemes 
presenting  every  bizarre  variety  of  figure,  with  strange 
complexities  of  spiral  whorls  or  outlying  branches, 
losing  themselves,  as  it  were,  in  the  depths  toward 
which  they  seem  to  extend — this  also  need  not  sur- 
prise us :  we  need  not  conclude  that  here,  at  any  rate, 
we  are  looking  beyond  the  bounds  of  the  sidereal  sys- 
tem, and  gazing  upon  external  galaxies,  for  the  anal- 
ogy we  have  chosen  for  our  guidance  teaches  us  that 
such  structures  were  to  be  expected  within  the  scheme 
of  which  our  sun  is  a  component.  And,  finally,  if  we 


Z36  OTHER   WORLDS  THAN  OURS. 

should  find  reason  to  assure  ourselves  that  there  are 
objects  in  the  depths  of  space  whose  very  substance 
and  constitution  are  different  from  those  of  all  other 
objects  within  the  sidereal  system,  we  need  by  no 
means  believe  that  the  objects  thus  singularly  consti- 
tuted belong  to,  or  form,  external  systems.  For  the 
millions  on  millions  of  comets  which  form  part  and 
parcel  of  the  solar  system  present  a  precisely  analogous 
difference  of  structure,  as  compared  with  the  other 
members  of  that  system. 

Having  thus  replaced  the  erroneous  analogies  to 
which — through  no  fault  of  his  own — Sir  William 
Herschel  was  led  to  look  for  guidance,  by  the  more 
trustworthy  analogies  which  the  recent  progress  of 
astronomy  has  afforded  for  our  instruction,  we  may 
proceed  to  consider  the  direct  evidence  we  have  re- 
specting the  constitution  of  our  galaxy. 

In  the  first  place,  let  us  examine  the  evidence 
which  points  to  the  dimensions  of  the  sidereal  system. 

That  the  nearest  members  of  the  system  lie  at 
enormous  distances  from  us  is  proved  by  the  fact  that, 
as  the  earth  sweeps  on  her  vast  orbit  round  the  sun, 
no  appreciable  change  is  observed  in  the  configuration 
of  the  star-groups.  That  a  circle  having  a  diameter  of 
more  than  one  hundred  and  eighty  millions  of  miles 
should  be  swept  out  year  by  year  as  the  earth  trav- 
erses her  orbit,  and  yet  that  the  surrounding  stars 
should  exhibit  no  change  of  place,  is  at  once  the  most 
striking  and  the  simplest  evidence  we  have,  of  the 
enormous  scale  on  which  the  sidereal  system  is  con- 
structed. And  yet  this  first  obvious  fact  sinks  almost 


OTHER  SUNS  THAN  OURS.  237 

into  insignificance  when  we  regard  thoughtfully  the 
teaching  of  modern  instrumental  astronomy.  There 
might  be  a  real  shifting  of  apparent  position  which 
yet  the  unaided  eye  would  fail  to  detect,  and  such  a 
change  would  indicate  distances  so  enormous  that  the 
mind  fails  altogether  to  conceive  their  real  signifi- 
cance. But  the  exact  instruments  of  modern  times 
would  exhibit  a  change  of  place  infinitely  more  mi- 
nute than  any  which  the  unaided  eye  could  recognize. 
If  a  star  shifted  by  so  much  as  the  ten  thousandth  part 
of  the  moon's  apparent  diameter,  modern  astronomers 
could  assure  themselves  of  the  change  of  place.  And 
when  we  remember  that  in  precisely  the  same  propor- 
tion that  we  increase  the  exactitude  of  instrumental 
observation  we  increase  also  the  significance  of  the 
stars'  apparent  fixity  of  position,  it  will  be  seen  at  once 
how  astounding  is  the  lesson  conveyed  by  the  fact 
that  all  but  a  very  few  indeed  of  the  stars  remain  abso- 
lutely unaffected — even  under  the  most  powerful  in- 
strumental examination — by  the  enormous  range  of 
the  earth's  orbital  motion. 

We  can  roughly  estimate  the  distances  of  the  few 
stars  which  are  thus  affected,  and  thence — on  the  hy- 
pothesis that  the  intrinsic  brilliancy  of  their  light  is 
the  same  as  the  sun's — we  may  form  some  idea  of 
their  dimensions.  I  shall,  however,  only  apply  this 
process,  in  detail,  to  a  single  case,  because  my  present 
object  is  rather  to  indicate  in  a  general  way  the  scale 
on  which  the  sidereal  system  is  constructed,  than  to 
enter  at  length  on  the  more  exact  details  which  fin*! 
their  place  in  ordinary  treatises  on  astronomy. 


Z38  OTHER   WORLDS  THAN  OURS. 

The  star  Alpha  Centauri  is  one  of  the  brightest  in 
the  heavens,  Sirius  and  Canopus  alone  surpassing  it 
in  splendor.  But  it  is  not  its  exceptional  brilliancy 
alone  which  led  astronomers  to  regard  it  as  likely  to 
afford  evidence  of  an  apparent  change  of  place  corre- 
sponding to  the  earth's  real  change  of  place  as  she 
sweeps  round  her  orbit.  Of  course,  the  brightest 
stars  are  presumably  the  nearest ;  but  there  is  another 
indication  of  proximity  at  least  equally  important. 
The  so-called  fixed  stars  are  in  reality  slowly  moving 
onward  on  definite  courses — slowly,  that  is,  in  appear- 
ance, though  in  reality  their  motions  are  doubtless 
inconceivably  rapid.  Now,  these  motions,  the  proper 
motions  of  the  stars,  as  they  are  called,  are  as  yet  very 
little  understood.  "We  know  only  that  the  whole  of 
the  galactic  system  is  astir  with  life,  but  whither  the 
orbs  are  severally  tending  we  are  not  yet  able  to  say. 
Nor  do  we  know  what  portion  of  the  stellar  motions 
may  be  due  to  the  undoubted  proper  motion  of  our 
own  sun  through  space.  This,  however,  may  be  re- 
garded as  certain,  that,  until  we  know  something  re- 
specting the  laws  which  regulate  the  stellar  move- 
ments, we  must  regard  the  magnitude  of  a  star's 
motion  as  probably  an  indication  of  relative  proxim- 
ity. Precisely  as  a  man  walking  at  a  great  distance 
from  us  appeal's  to  move  much  more  slowly  than  one 
who  is  walking  at  the  same  rate  close  by,  so  the  ap- 
parent rate  of  a  star's  motion  is  diminished  in  propor- 
tion to  the  star's  distance  from  us.  When,  therefore, 
it  was  found  that  the  star  Alpha  Centauri  is  moving 
more  rapidly  than  other  stars,  this  fact,  combined  with 


OTHER  SUNS  THAN  OURS. 


239 


the  great  lustre  of  the  star,  led  astronomers  to  suspect 
that  it  must  be  comparatively  near  to  us. 

Observations,  made  to  determine  whether  the  star 
shows  any  sign  of  an  annual  change  of  place  corre- 
sponding to  the  earth's  annual  orbital  motion,  were 
rewarded  by  the  detection  of  a  very  appreciable  dis- 
placement. In  fact,  owing  to  the  motion  of  the  earth, 
each  year,  in  a  nearly  circular  orbit  one  hundred  and 
eighty  million  miles  in  diameter,  the  star  Alpha  Cen- 
tauri  appears  to  trace  out  each  year  a  minute  oval  patli 
on  the  celestial  sphere,  the  greater  axis  of  the  oval  be- 
ing equal  in  length  to  about  -g-^-g-th  part  of  the  moon's 
apparent  diameter.* 

It  follows  from  this  that,  in  round  numbers,  the 
distance  of  Alpha  Centauri  from  us  is  about  twenty 
millions  of  millions  of  miles.  The  distance  of  the 
earth  from  the  sun  shrinks  into  insignificance  beside 
this  enormous  gap.  Even  Neptune,  though  circling 
round  the  sun  at  a  distance  three  hundred  times  vaster 
than  that  which  separates  us  from  that  luminary,  is 
yet  relatively  so  much  nearer  than  Alpha  Centauri, 
that  a  sun  filling  the  whole  orbit  of  Neptune  would 
appear,  as  seen  from  that  star,  but  about  one-ninth  as 
large  as  the  sun  appears  to  us. 

Now  let  us  consider  what  dimensions  we  may  as- 
sign to  Alpha  Centauri,  on  the  assumption  that  the 
surface  of  this  star  emits  a  light  as  brilliant  as  that 

*  It  hardly  need  be  mentioned,  perhaps,  that  this  motion  being 
Buperadded  to  the  star's  more  considerable  proper  motion,  the  path 
which  the  star  seems  really  to  follow  is  a  looped  one,  the  size  of  each 
loop  being  small  hi  comparison  with  the  distance  between  successive 
loops. 


240  OTHER   WORLDS  THAN  OURS. 

which  proceeds  from  the  photosphere  of  our  own  sun. 
We  must  not  neglect  the  consideration  that  the  star  is 
double — the  companion  emitting  perhaps  about  one- 
sixteenth  as  much  light  as  the  primary.*  The  distance 
of  Alpha  Centauri  is  equal  to  about  two  hundred  and 
thirty  thousand  times  that  which  separates  us  from  the 
sun.  Therefore,  if  removed  to  the  star's  distance,  the 
sun  would  shine  with  only  ^^^th  part  of  his  present 
brilliancy.  Now,  according  to  the  most  careful  esti- 
mates of  the  brilliancy  of  Alpha  Centauri,  the  light 
we  receive  from  that  star  is  about  ^^^^th  of  that  we 
receive  from  the  sun.f  It  follows,  therefore,  that  the 
star  emits  about  three  times  as  much  light  as  the  sun ; 
and  therefore,  so  far  as  the  emission  of  light  is  a  crite- 
rion of  size,  the  star  may  be  regarded  as  considerably 
larger  than  our  own  sun.  In  fact,  reducing  the  total 
light  of  the  pair  by  one-sixteenth,  we  find  that  the 
primary  must  still  emit  about  three  times  as  much 
light  as  the  sun,  and  therefore  the  diameter  of  the 
star,  as  thus  estimated,  would  appear  to  exceed  our 
sun's  in  the  proportion  of  about  seventeen  to  ten. 

We  have  here,  then,  clear  and  decisive  evidence  in 
favor  of  the  view  that  among  the  fixed  stars  there  are 
orbs  which  may  be  regarded  as  veritable  suns,  worthy 
to  be  the  ruling  centres  of  schemes  as  noble  as  the  solar 

*  Sir  John  Herschel,  observing  the  star  with  his  twenty-feet  reflector, 
thought  the  secondary  brighter  than  it  is  usually  considered.  I  cannot 
but  think  that,  for  a  comparison  of  this  sort,  smaller  telescopes  may  more 
safely  be  trusted. 

f  This  estimate  is  founded  on  Sir  John  Herschel's  comparison  be- 
tween the  light  of  the  star  and  that  of  the  full  moon,  and  Zollner'a 
comparison  between  the  light  of  the  full  moon  and  that  of  the  sun. 


OTHER  SUNS  THAN  OURS.  24 ! 

system.  For  we  know  quite  certainly  that  the  greater 
number  of  the  first-magnitude  stars  are  very  much 
farther  from  us  than  Alpha  Centauri,  with  which,  how- 
ever, they  are  fairly  comparable  in  brilliancy :  so  that 
they  may  be  regarded  as  for  the  most  part  at  least 
equal  to  that  star  in  size  and  mass.  Sirius  and  Canopus, 
indeed,  must  far  surpass  Alpha  Centauri.  The  latter, 
though  more  than  thrice  as  bright,  exhibits  no  appre- 
ciable change  of  position  as  the  earth  circles  round  the 
sun.  Sinus,  which  is  more  than  four  times  brighter 
than  Alpha  Centauri,  shows  an  annual  change  of  posi- 
tion which  certainly  does  not  exceed  one-fourth  of  that 
star's.  It  is  therefore  four  times  farther  from  us  than 
Alpha  Centauri,  and,  did  it  emit  no  greater  amount 
light,  would  appear  to  shine  with  but  one-sixteenth 
of  that  star's  lustre.  As  in  reality  it  is  four  times  as 
bright,  the  real  amount  of  light  it  emits  must  exceed 
that  of  Alpha  Centauri  no  less  than  sixty-four  times, 
and  that  of  our  own  sun  no  less  than  one  hundred  and 
ninety-two  times.  So  that,  judged  from  this  indication 
alone,  the  diameter  of  Sirius  may  be  held  to  exceed 
that  of  our  sun  in  the  proportion  of  about  fourteen  to 
one,  an  estimate  which  assigns  to  Sirius  a  diameter  of 
nearly  twelve  million  miles,  and  a  volume  two  thou- 
sand six  hundred  and  eighty-eight  times  as  large  as  the 
sun's. 

But,  on  the  other  hand,  still  confining  our  atten- 
tion to  this  method  of  estimating  magnitude,  we  find 
reason  for  believing  that  many  of  the  visible  stars 
must  fall  far  short  of  our  sun  in  magnitude.  The 
sixth-magnitude  double  star,  61  Cygni,  has  been  found 
11 


2^.2  OTHER    WORLDS  THAN  OURS. 

to  be  nearer  to  us  than  Sirius,  and  about  three  times 
as  far  from  us  as  Alpha  Centauri.  Now,  we  may  as- 
sume that  each  component  sends  us  about  one-hun- 
dredth part  of  the  light  we  receive  from  Alpha  Cen- 
tauri ;  it  follows  that  the  latter  star,  if  removed  to 
the  distance  at  which  61  Cjgni  lies  from  us  (when  its 
light  would  of  course  be  diminished  to  one-ninth  of  its 
present  value),  would  outshine  either  component  of 
that  double  star  more  than  eleven  times ;  hence  (on 
the  assumption  that  brightness  is  a  fair  measure  of  real 
dimensions),  each  component  has  a  diameter  less  than 
one-third  that  of  Alpha  Centauri.  We  may  roughly 
estimate  the  volume  of  each  at  about  -^th  of  that  of 
the  latter  star.  So  that,  remembering  what  has  al- 
ready been  shown  respecting  the  relation  between 
Alpha  Centauri  and  our  sun,  the  two  suns  which  form 
the  double  star  61  Cygni  would  each  have  a  diameter 
equal  to  about  -^ths  of  the  sun's,  and  a  volume 
equal  to  about  -^ths.  The  sum  of  their  volumes  would 
be  therefore  about  one-third  of  his ;  and  it  will  presently 
appear  that  a  perfectly  distinct  mode  of  estimation 
tends  to  show  that  the  sum  of  their  masses  bears  about 
the  same  proportion  to  the  sun's  mass. 

But  here  at  once  we  have  evidence  that  there  is  a 
very  wide  range  of  magnitude  among  the  fixed  stars. 
We  have  seen  reason  to  believe  that  Sirius  is  twenty- 
six  hundred  and  eighty-eight  times  as  large  as  the 
sun,  while  each  of  the  suns  forming  the  double  star 
61  Cygni  would  appear  to  have  a  volume  less  than 
one-fifth  of  our  sun's,  and  therefore  less  than  Tsf^nrth 
of  the  volume  of  Sirius.  So  that,  by  considering 


OTHER  SUNS  THAN  OURS.         24.3 

only  three  cases,  we  have  found  tolerably  clear  evi- 
dence of  a  range  of  variety  in  volume,  reminding  us 
forcibly  of  that  which  we  recognize  in  the  solar  system. 
"We  cannot  suppose  that  these  three  cases,  which  have 
been  selected  at  random — so  far  as  the  question  of  vol- 
ume is  concerned — indicate  any  thing  like  the  real 
limits  within  which  the  fixed  stars  differ  in  magnitude. 
So  that  we  may  confidently  accept,  as  the  most  prob- 
able conclusion  from  the  evidence  before  us,  that  the 
range  of  real  magnitude  among  the  fixed  stars  is  very 
far  greater  than  Sir  W.  Herschel  was  led  to  anticipate, 
when,  nearly  a  century  ago,  he  began  his  researches 
into  the  sidereal  system. 

But  it  is  not  sufficient  that  we  should  thus  form 
an  estimate  of  the  nature  of  the  fixed  stars,  from  the 
amount  of  light  they  send  to  us.  It  is  desirable — and 
fortunately  it  is  practicable — to  obtain  information  as 
to  the  absolute  mass  or  weight  of  some  of  the  fixed 
stars,  and  further  to  ascertain  of  what  substances  they 
may  be  composed,  and  in  what  condition  those  sub- 
stances may  exist.  Mere  lights,  however  glorious,  or 
however  wide  the  sphere  within  which  they  displayed 
their  splendors,  would  not  be  fit  to  sway  the  motions 
of  orbs  resembling  those  which  circle  around  our  sun. 
Nor  would  such  lights  serve  to  indicate  to  the  astron- 
omer that,  out  yonder,  myriads  of  millions  of  miles 
beyond  the  extreme  limits  of  the  solar  system,  there 
exist  materials  suited  to  form  the  substance  of  worlds 
resembling  our  own. 

It  seems  a  strange  circumstance  that  astronomers 
should  be  able  to  form  a  more  exact  and  trustworthy 


2^4  OTHER   WORLDS  THAN  OURS. 

estimate  of  the  weight  of  certain  fixed  stars  than  they 
can  hope  to  form  respecting  the  volume  of  any  of  those 
bodies.  Let  us  consider  what  evidence  we  have  on 
this  point. 

I  have  spoken  of  the  star  61  Cygni  as  a  double 
star.  The  smaller  star  shows  very  clear  indica- 
tions of  orbital  motion  around  its  primary.  That  the 
two  are  associated  together,  and  not  merely  seen,  as  it 
were  by  an  accident,  nearly  in  the  same  line  of  view, 
is  indeed  certain,  because  that  peculiarly  large  prop- 
er motion  already  referred  to  is  shared  in  by  both. 
But  many  stars  may  be  physically  associated,  and  yet 
the  distance  really  separating  them  may  enormously 
exceed  that  by  which  they  seem  to  be  separated — 
since  the  line  joining  them  is  not  necessarily  square 
to  the  line  of  sight.  The  components  of  the  star  61 
Cygni  have  been  carefully  watched,  however,  and  their 
motions  show  that  they  are  circling  around  each  other. 
The  distance  separating  them  is  probably  about  half 
as  large  again  as  the  distance  of  Neptune  from  the 
sun. 

The  period  of  revolution  appears  to  be  about  five 
hundred  and  twenty  years,  which  is  more  than  three 
times  as  great  as  the  period  of  Neptune.  Now,  we 
know  that  a  planet  placed  at  distance  from  the  sun, 
equal  to  that  which  separates  the  components  of  61 
Cygni,  would  occupy  a  much  less  period  than  five  hun- 
dred and  twenty  years  in  completing  a  revolution ;  in 
fact,  its  period  would  be  about  three  hundred  years. 
Hence  it  follows  that  the  components  of  61  Cygni  are  at- 
tracted together  less  forcibly  than  Neptune  is  attracted 


OTHER  SUNS  THAN  OURS.  245 

toward  the  sun,  and  therefore  that  the  sum  of  their 
masses  must  be  less  than  the  sun's  mass.  It  is  easy 
to  compute  the  actual  proportion,  and  we  find  accord- 
ingly that  the  two  components  of  61  Cygni,  taken  to- 
gether, weigh  about  one-third  as  much  as  our  sun.* 

The  star  Alpha  Centauri  is  also  a  binary  system, 
and,  though  it  has  not  been  so  systematically  observed 
as  61  Cygni,  some  astronomers  believe  that  its  period 
has  been  even  more  satisfactorily  determined.  Indeed, 
there  are  peculiarities  in  the  motion  of  61  Cygni, 
which,  without  throwing  doubt  on  the  general  conclu- 
sions deduced  above,  yet  suggest  that  a  third  (proba- 
bly opaque)  orb  affects  the  motions  of  the  other  two. 
From  a  careful  comparison  of  all  the  observations 
made  in.  recent  times  on  Alpha  Centauri,  Mr.  Hind 
has  assigned  to  the  components  a  period  of  revolu- 
tion of  about  eighty-one  years,  and  a  mean  distance  of 
13.6  seconds  of  arc,  corresponding  to  a  real  distance 
exceeding  the  earth's  distance  from  the  sun  some  fif- 
teen times.  Since  a  planet  placed  at  this  distance 
from  the  sun  would  occupy  less  than  sixty  years  in 
completing  a  revolution  around  that  body,  it  follows 
that  the  mass  of  the  two  components  of  Alpha  Cen- 
tauri must  be  less  than  that  of  the  sun.  This  result 
(if  the  data  be  considered  trustworthy)  would  indicate 
a  considerable  difference  between  the  condition  of  the 
star  and  that  of  our  sun ;  for  we  have  seen  that  the 

*  It  may  easily  be  shown  that,  if  a  pair  of  bodies,  circling  around 
each  other  at  a  certain  distance,  take  a  certain  tune  T  in  effecting  a 
revolution,  while  another  pair  at  the  same  distance  take  a  time  t,  the 
former  pair,  taken  together,  have  a  weight  which  bears  to  the  weight  of 
ihe  latter  pair  the  ratio  of  P  to  T*. 


146  OTHER   WORLDS  THAN  OURS. 

star  gives  out  much  more  light  than  the  sun.  How- 
ever, I  believe  that  many  years  must  elapse  before  we 
can  regard  the  period  of  Alpha  Centauri  as  satisfac- 
torily determined. 

Still,  we  have  conclusive  evidence  in  this  case,  as 
in  that  of  the  star  61  Cygni,  that  the  component 
stars  are  really  bodies  of  enormous  weight,  and  conse- 
quently well  fitted  to  sway  the  motions  of  families  of 
planets.  We  conclude,  therefore,  that  the  fixed  stars 
generally  are  suns,  not  mere  lights  /  and,  further,  we 
are  led  to  believe  that  there  must  be  a  general  similar- 
ity in  the  conditions  under  which  these  bodies  and  our 
own  sun  emit  light.  And  thus  we  are  led  to  recognize 
other  stars  also — though  as  yet  unweighed — as  mas- 
sive orbs,  not  merely  supplying  light  to  other  worlds 
travelling  around  them,  but  regulating  by  their  attrac- 
tive influences  the  orbital  motions  of  their  dependent 
worlds. 

But  we  owe  to  the  revelations  of  the  spectroscope 
the  complete  proof  of  these  matters,  besides  evidence 
on  other  and  equally  interesting  points. 

It  had  long  been  known  that  the  spectra  of  the  fixed 
stars  present  a  general  resemblance  to  the  solar  spec- 
trum, though  of  course  very  much  fainter,  and  that 
dark  lines  can  be  seen  in  these  spectra,  some  of  which 
correspond  with  those  in  the  sun's  spectrum,  while 
others  seem  to  be  new.  So  soon  as  the  great  discovery 
effected  by  Kirchhoff  had  been  announced,  it  was  seen 
at  once  that  these  dark  lines  in  the  stellar  spectra  af- 
ford the  means  of  determining  the  constitution  of  the 
stars.  It  was  only  necessary  that  these  lines  should 


OTHER  SUNS  THAN  OURS.  2^ 

be  identified  by  their  correspondence  with  the  lines 
belonging  to  known  elements,  in  order  to  prove  that 
these  elements  exist  in  the  substance  of  the  star.  But, 
although  the  principle  on  which  researches  were  to  be 
conducted  was  sufficiently  simple,  many  difficulties 
had  to  be  encountered.  Indeed,  the  attempts  made 
by  Airy,  Secchi,  and  Kutherford,  to  solve  the  problem 
of  determining  the  constitution  of  the  stars  by  means 
of  spectroscopic  analysis,  were  unsuccessful ;  and  it 
was  not  until  Prof.  Miller  and  Mr.  Huggins  commenced 
their  famous  series  of  researches  that  the  problem  can 
be  said  to  have  been  fairly  mastered. 

Even  in  the  hands  of  these  eminent  physicists  the 
work  was  difficult,  and  its  progress  tedious.  The 
weather  necessary  for  the  successful  prosecution  of  so 
delicate  a  method  of  inquiry  does  not  often  prevail  in 
our  variable  climate.  The  comparison  between  the 
dark  lines  in  the  stellar  spectra  and  the  bright  lines 
belonging  to  various  elements  was  not  only  a  delicate 
and  laborious  task,  but  was  singularly  painful  to  the 
eyes.  And  other  difficulties,  into  which  I  have  not 
space  to  enter  here,  had  to  be  encountered  and  over- 
come. 

But,  undeterred  by  these  difficulties,  the  two  physi- 
cists persevered  in  their  researches,  and  were  rewarded 
by  results  so  interesting  and  important  that  their  dis- 
covery may  be  said  to  constitute  the  most  remarkable 
era  in  the  history  of  sidereal  research  since  the  com- 
pletion of  the  star-gaugings  of  the  elder  Herschel. 

Two  bright  stars,  Betelgeux,  the  leading  brilliant 
of  Orion,  and  Aldebaraii,  the^chief  star  of  Taurus, 


248  OTHER   WORLDS  THAN  OURS. 

were  examined  with  special  care.  Mr.  Huggins  re- 
marks that  the  spectra  of  these  stars  are  as  rich  in 
lines  as  the  solar  spectrum  itself.  The  places  of  no 
less  than  eighty  lines  in  the  spectrum  of  Betelgeux 
were  accurately  measured,  while  as  many  as  seventy 
lines  had  their  places  assigned  to  them  in  the  spectrum 
of  Aldebaran. 

"With  respect  to  the  former  spectrum,  Mr.  Huggins 
remarks  that  it  is  most  complex  and  remarkable. 
"  Strong  groups  of  lines  are  visible,  especially  in  the 
red,  the  green,  and  the  blue  portions,"  a  peculiarity,  it 
may  be  remarked  in  passing,  which  serves  to  account 
for  the  well-marked  orange-color  of  this  star. 

Now,  here  already  we  have  very  decided  evidence 
as  to  the  nature  of  the  star ;  since  the  very  fact  that 
its  spectrum  presents  the  same  general  appearance  as 
the  solar  spectrum,  proves  conclusively  that  the  star  is 
an  incandescent  body,  whose  light  comes  to  us  through 
certain  vapors  corresponding  to  those  which  surround 
the  sun.  Nor  should  we  be  able  to  regard  the  star  ac 
other  than  a  sun,  even  though  none  of  the  elements 
known  to  us  should  appear  to  be  present  in  its  sub- 
stance, or  in  the  vapors  surrounding  it.  For,  clearly, 
we  have  no  reason  for  believing  that  worlds  can  be 
formed  out  of  those  elements  only  witli  which  we  are 
acquainted,  unless  we  find,  as  we  proceed,  that  those 
elements  actually  do  compose  the  suns  which  form  the 
sidereal  system.  Of  course,  if  this  shall  appear  to  be 
the  case,  our  conclusions  respecting  the  nature  of  the 
stars  will  be  very  much  strengthened. 

Now,  when  Prof.  Miller  and  Mr.  Huggins  com- 


OTHER  SUNS  THAN  OURS.  249 

pared  the  lines  in  the  spectrum  of  Betelgeux  with  the 
bright  lines  of  certain  terrestrial  elements,  they  found 
that  some  of  these  elements  do  actually  exist  in  the 
vaporous  envelope  of  the  stars.  Thus,  sodium,  mag- 
nesium, calcium,  iron,  and  bismuth,  are  present  in 
Betelgeux.  The  lines  of  hydrogen,  which  are  so  well 
marked  in  the  solar  spectrum,  are  not  seen  in  the  spec- 
trum of  Betelgeux.  "We  are  not  to  conclude  from  this 
that  hydrogen  does  not  exist  in  the  composition  of  the 
star.  "We  know  that  certain  parts  of  the  solar  disk, 
when  examined  with  the  spectroscope,  do  not  at  all 
times  exhibit  the  hydrogen  lines,  or  may  even  present 
them  as  bright  instead  of  dark  lines.  It  may  well  be 
that  in  Betelgeux  hydrogen  exists  under  such  condi- 
tions that  the  amount  of  light  it  sends  forth  is  nearly 
equivalent  to  the  amount  it  absorbs,  in  which  case  its 
characteristic  lines  would  not  be  easily  discernible. 
In  fact  it  is  important  to  notice  generally,  that,  while 
there  can  be  no  mistaking  the  positive  evidence  af- 
forded by  the  spectroscope  as  to  the  existence  of  any 
element  in  sun  or  star,  the  negative  evidence  supplied 
by  the  absence  of  particular  lines  is  not  to  be  certainly 
relied  upon. 

In  the  case  of  Aldebaran  the  two  physicists  were 
able  to  establish  the  existence  of  sodium,  magnesium, 
hydrogen,  calcium,  iron,  bismuth,  tellurium,  antimony, 
and  mercury,  in  the  vapors  surrounding  the  star. 

Besides  these  stars,  fifty  others  were  examined. 
The  brilliant  Sirius  exhibits  a  spectrum  of  great  beau- 
ty, though  the  low  altitude  which  this  star  attains  in 
our  latitudes  rendered  the  observation  of  the  finer 


i$0  OTHER   WORLDS  THAN  OURS. 

lines  exceedingly  difficult.  But  the  two  physicists 
were  able  to  show  that  sodium,  magnesium,  hydrogen, 
and  probably  iron,  exist  in  this  gigantic  sun. 

All  the  stars  examined  exhibit  spectra  crossed  by 
numerous  lines ;  and,  in  a  great  number  of  the  spectra, 
lines  belonging  to  known  terrestrial  elements  were  de- 
tected. 

And  now  let  us  consider  the  general  bearing  of 
these  interesting  discoveries. 

In  the  first  place,  we  are  forced  to  recognize  in  the 
stars  real  suns,  not  mere  lights.  Doubtless  Dr.  "Whe- 
well  did  well  in  pointing  out  that  astronomers  had  no 
right  to  regard  the  stars  as  suns,  until  they  had  some 
evidence  that  these  orbs  resemble  the  sun  in  other  re- 
spects than  in  size,  mass,  or  luminosity.  And  as  in 
his  day  it  appeared  altogether  unlikely  that  such  evi- 
dence should  be  obtained,  a  real  limit  seemed  placed 
to  the  speculations  men  might  form  as  to  the  existence 
of  other  planetary  systems  besides  those  which  circle 
around  the  sun. 

But  now  we  have  precisely  that  evidence  which 
Whewell  required.  "We  see  that  the  stars  are  consti- 
tuted in  the  same  general  way  as  the  sun,  and  that, 
further,  they  even  contain  elements  identical  with 
those  which  exist  in  his  substance.  There  is  not  in- 
deed in  every  case,  perhaps  there  may  not  be  in  any 
case,  an  exact  identity  of  composition  between  star  and 
sun,  or  between  star  and  star.  But  this  was  no  more  to 
have  been  looked  for  than  an  exact  identity  of  physi- 
cal habitudes  among  the  members  of  the  solar  system. 
That  general  resemblance  of  structure  which  indicates 


OTHER  SUNS  THAN  OURS.  25, 

a  general  resemblance  in  the  purposes  which  the  ce- 
lestial bodies  are  intended  to  subserve,  is  undoubtedly 
evident,  when  we  compare  the  stars  either  with  our 
sun  or  with  each  other. 

I  have  already  spoken  of  the  conclusions  to  be 
drawn  from  the  existence  of  the  same  materials  in  the 
substance  of  the  sun  that  exist  around  us  on  this 
earth.  I  have  shown  that  we  are  compelled  to  regard 
this  general  resemblance  of  structure  as  sufficient  to 
prove  that  the  other  planets  resemble  the  earth,  since 
we  have  no  reason  to  believe  that  our  earth  bears  an 
exceptionally  close  resemblance  to  the  sun  as  respects 
the  elements  of  which  she  is  composed. 

Since,  then,  we  have  reason  to  believe  that  all  the 
planets  which  circle  around  the  sun  are  constituted 
of  the  same  materials  which  exist  in  his  substance, 
though  these  materials  are  not  necessarily  nor  proba- 
bly combined  in  the  same  proportions  throughout  the 
solar  system,  we  have  every  reason  which  analogy  can 
give  us  for  believing  that  the  planets  circling  around 
Betelgeux  or  Aldebaran  are  constituted  of  the  same 
materials  which  exist  in  the  substance  of  their  central 
luminary. 

Thus  we  are  led  to  a  number  of  interesting  con- 
clusions even  respecting  orbs  which  no  telescope  that 
man  can  construct  is  likely  to  reveal  to  his  scrutiny. 
The  existence  of  such  elements  as  sodium  or  calcium 
in  those  other  worlds  suggests  the  probable  existence 
of  the  familiar  compounds  of  these  metals — soda,  salt, 
lime,  and  so  on.  Again,  the  existence  of  iron  and 
other  metals  of  the  same  class  carries  our  minds  to  the 


^2        OTHER  WORLDS  THAN  OURS. 

various  useful  purposes  which  these  metals  are  made 
to  subserve  on  the  earth.  We  are  at  once  invited  to 
recognize  that  the  orbs  circling  around  those  distant 
suns  are  not  meant  merely  to  be  the  abode  of  life,  but 
that  intelligent  creatures,  capable  of  applying  these 
metals  to  useful  purposes,  must  exist  in  those  worlds. 
We  need  not  conclude,  indeed,  that  at  the  present 
moment  every  one  of  those  worlds  is  peopled  with  in- 
telligent beings,  because  we  have  good  reason  for  be- 
lieving that  throughout  an  enormous  proportion  of 
the  time  during  which  our  earth  has  existed  as  a 
world  no  intelligent  use  has  been  made  of  the  supplies 
of  metal  existing  in  her  substance.  But  that  at  some 
time  or  other  those  worlds  have  been  or  will  be  the 
abode  of  intelligent  creatures  seems  to  be  a  conclusion 
very  fairly  deducible  from  what  we  now  know  of  their 
probable  structure. 

But,  secondly,  apart  from  the  information  aiforded 
by  the  spectroscope  respecting  the  materials  of  which 
the  stars  are  composed,  the  nature  of  the  stellar  spec- 
tra serves  to  prove  most  conclusively  that  the  stars, 
besides  supplying  light  to  the  worlds  which  circle 
around  them,  radiate  heat  also  to  them.  Even  if  we 
were  not  certain  that  elements  which  are  only  vapor- 
ized at  a  very  high  temperature  exist  in  the  vaporous 
envelopes  of  the  stars,  yet  the  very  nature  of  the  light 
sent  out  by  the  stars  indicates  that  these  orbs  are  in- 
candescent through  intensity  of  heat.  When  we  find 
that  the  spectrum  of  a  planet's  light  resembles  the 
solar  spectrum,  we  do  not  indeed  conclude  that  the 
planet  is  as  intensely  heated  as  the  sun,  because  we 


OTHER  SUNS  THAN  OURS.         2$} 

know  that  the  planets  are  not  self-luminous.  But,  in 
the  case  of  self-luminous  bodies  like  the  stars,  we  can 
conclude  from  the  very  nature  of  their  spectra  that 
these  orbs  are  intensely  heated.  Of  course  we  are 
rendered  absolutely  certain  of  this  when  we  find  that 
iron  and  other  metals  exist  in  the  form  of  vapor  in  the 
stellar  atmospheres. 

The  vast  supplies  of  heat  thus  emitted  by  the  stars 
not  only  suggest  the  conclusion  that  there  must  be 
worlds  around  these  orbs  for  which  those  heat-supplies 
are  intended,  but  point  to  the  existence  in  those 
worlds  of  the  various  forms  of  force  into  which  heat 
may  be  transmuted.  We  know  that  the  sun's  heat 
poured  upon  our  earth  is  stored  up  in  vegetable  and 
animal  forms  of  life  ;  is  present  in  all  the  phenomena 
of  Nature — in  winds,  and  clouds,  and  rain,  in  thunder 
and  lightning,  storm  and  hail;  and  that  even  the 
works  of  man  are  performed  by  virtue  of  the  solar 
heat-supplies.  Thus  the  fact,  that  the  stars  send  forth 
heat  to  the  worlds  which  circle  around  them,  suggests 
at  once  the  thought  that  on  those  worlds  there  must 
exist  vegetable  and  animal  forms  of  life ;  that  natural 
phenomena,  such  as  we  are  familiar  with  as  due  to  the 
solar  heat,  must  be  produced  in  those  worlds  by  the 
heat  of  their  central  sun;  and  that  works  such  as 
those  which  man  undertakes  on  earth  —  works  in 
which  intelligent  creatures  use  Nature's  powers  to 
master  Nature  to  their  purposes — must  go  on  in  the 
worlds  which  circle  around  Aldebaran  and  Betelgeux, 
around  Yega,  Capella,  and  the  blazing  Sirius. 

Recently  it  has  even  been  found  possible  to  render 


Z54  OTHER    WORLDS  THAN  OURS. 

the  stellar  heat  sensible  to  terrestrial  observation,  by 
methods  which  need  not  here  be  inquired  into.  Nay, 
the  task  of  measuring  the  amount  of  heat  received 
from  certain  stars  has  not  been  thought  too  difficult. 
Mr.  Stone,  making  use  of  the  powers  of  the  great 
equatorial  of  the  Greenwich  Observatory,  and  inge- 
niously overcoming  the  numerous  difficulties  which 
exist  in  a  research  of  such  exceeding  delicacy,  has 
arrived  at  the  conclusion  that  Arcturus  sends  us  about 
as  much  heat  as  would  be  received  from  a  three-inch 
cube  full  of  boiling  water,  and  placed  at  a  distance  of 
three  hundred  and  eighty-three  yards.  Yega,  which 
shines,  according  to  Sir  J.  Herschel,  with  about  two- 
thirds  the  light  of  Arcturus,  gives  out  about  the  same 
proportionate  amount  of  heat.*  But  in  other  in- 
stances the  heat-giving  power  of  a  star  has  not  been 
found  proportional  to  the  amount  of  light  it  emits. 

The  variation  of  many  fixed  stars  in  lustre  at  once 
forms  a  new  bond  of  association  between  the  stars  and 

*  Although  these  results  cannot  yet  be  regarded  as  numerically  ex- 
act, it  may  be  interesting  to  consider  the  amount  of  heat  given  out  by 
Arcturus  in  relation  to  the  light  sent  us  by  this  star,  the  more  so  as  this 
star  seems  (from  the  nature  of  its  spectrum)  to  resemble  the  sun  very 
closely  in  constitution. 

The  light  sent  to  us  by  Arcturus  is  equal  to  about  three-fourths  of 
that  supplied  by  Alpha  Centauri,  or  about  rrnnra^nraCTRrth  part  of  the 
light  we  receive  from  the  sun.  Now,  Mr.  Stone  estimates  the  direct 
heating  effect  of  Arcturus  at  0°.00,000,127  Fahrenheit,  making  due  al- 
lowance for  the  effect  of  the  object-glass  in  concentrating  and  absorbing 
the  heat.  It  will  be  seen  at  once  that,  according  to  this  estimate,  the 
heating  power  of  Arcturus  bears  a  very  much  greater  proportion  to 
that  of  the  sun  than  the  respective  light-giving  powers  of  these  lu- 
minaries bear  to  each  other.  This  seems  to  throw  some  doubt  on  the 
correctness  of  the  estimate,  eithei  of  the  light-giving  or  of  the  heat-giv- 
ing power  of  the  star. 


OTHER  SUNS  THAN  OURS.  255 

the  sun — which  we  have  seen  to  be  in  reality  a  vari- 
able star — and  suggests  interesting  inquiries  as  to  the 
existence  of  variation  in  the  emission  of  heat.  Some 
of  the  stellar  variations  of  light  are  so  much  more 
marked  than  those  noticed  in  the  case  of  our  own  sun 
that  we  can  scarcely  conceive  how  creatures,  resem- 
bling any  with  which  we  are  acquainted,  could  endure 
the  effects  of  corresponding  important  variations  of 
heat ;  nay,  in  some  instances  we  seem  compelled  to 
withhold  our  belief  in  the  existence  of  habitable  sys- 
tems around  certain  fixed  stars.  The  star  Eta  Argus, 
for  example,  which  sometimes  blazes  out  with  a  light 
surpassing  that  of  any  of  the  stars  in  the  northern 
hemisphere,  while  at  other  times  it  falls  to  the  sixth 
magnitude,  can  hardly  be  regarded  as  fit  to  be  the 
centre  of  a  system  of  worlds.  I  pass  over  such  varia- 
ble stars  as  the  one  which  recently  blazed  out  in  the 
Northern  Crown,  because  in  a  case  of  this  sort  the  star 
may  be  regarded  as  really  a  small  orb,  and  its  sudden 
lustre  as  due  to  some  exceptional  occurrence,  leading 
(as  the  spectrum  of  the  star  seemed  to  show)  to  a  tem- 
porary conflagration.  But  Eta  Argus  and  Mira  Ceti 
seem  to  belong  to  a  different  category  altogether,  since 
it  is  probable  as  respects  the  former,  and  certain  as  re- 
spects the  latter,  that  their  appearance  as  stars  of  the 
leading  magnitudes  is  not  accidental,  but  part  of  a 
systematic  series  of  changes. 

It  remains  only  to  be  mentioned  that,  besides  light 
and  heat,  the  stars  emit  actinic  rays.  This  is  proved 
decisively  by  the  fact  that  the  stars  can  be  made  to 
photograph  themselves.  It  has  been  found,  however, 


t$6  OTHER   WORLDS  THAN  OURS. 

that  the  actinic  power  of  a  star,  like  its  heat-giving 
power,  is  not  by  any  means  proportional  to  the  star's 
light.  So  that  in  this  respect,  as  in  the  material  con- 
stitution of  the  stars,  we  find  specific  varieties  even 
amid  those  very  features  which  indicate  most  strik- 
ingly the  general  resemblance  which  exists  between 
the  suns  constituting  the  sidereal  system. 

To  sum  up  what  we  have  learned  so  far  from  the 
study  of  the  starry  heavens — we  see  that,  besides  our 
sun,  there  are  myriads  of  other  suns  in  the  immensity 
of  space ;  that  these  suns  are  large  and  massive  bodies, 
capable  of  swaying  by  their  attraction  systems  of 
worlds  as  important  as  those  which  circle  around  the 
Bun ;  that  these  suns  are  formed  of  elements  similar  to 
those  which  constitute  our  own  sun,  so  that  the  worlds 
which  circle  round  them  may  be  regarded  as  in  all 
probability  similar  in  constitution  to  this  earth ;  and 
that  from  those  suns  all  the  forms  of  force  which  we 
know  to  be  necessary  to  the  existence  of  organized 
beings  on  our  earth  are  abundantly  emitted.  Is  it 
not  reasonable  to  conclude  that  these  suns  have  not 
been  made  in  vain  ?  If  thoughtful  men  have  reasoned 
rightly  in  supposing  that  the  light  and  heat  poured  out 
by  the  sun  upon  the  planets  which  circle  around  him 
are  not  wasted — in  the  case  of  all  the  planets  except 
our  small  earth — by  being  shed  where  no  forms  of  life 
can  profit  by  those  abundant  supplies,  surely  the  argu- 
ment is  a  million-fold  stronger  in  the  case  of  the  fixed 
stars.  Though  here  we  cannot,  as  in  the  case  of  the 
solar  system,  actually  see  the  worlds  about  which  we 
speculate,  yet  the  mind  presents  them  clearly  before 


OTHER  SUNS  THAN  OURS.  257 

us,  various  in  size,  various  in  structure,  infinitely  vari- 
ous in  their  physical  condition  and  habitudes,  bu 
alike  in  this,  that  each  is  peopled  by  creatures  per- 
fectly adapted  to  the  circumstances  surrounding  them, 
and  that  each  exhibits  in  the  clearest  and  most  strik- 
ing manner  the  wisdom  and  beneficence  of  the  Al- 
mighty. 


CHAPTER  XL 

OF   MINOR    STAES,    AND   OF   THE  DISTRIBUTION   OF 
IN   SPACE. 


IT  has  been  so  long  a  received  opinion  that  a  gen- 
eral uniformity  of  magnitude  and  distribution  charac- 
terizes the  stellar  system  that  it  is  with  some  diffi- 
dence I  venture  to  express  a  different  view.  And  here 
let  me  not  be  misunderstood.  I  am  fully  sensible 
that  it  is  only  in  certain  popular  treatises  of  astron- 
omy that  a  belief  in  any  thing  like  a  real  uniformity  of 
structure  in  the  sidereal  system  is  attributed  to  astron- 
omers of  authority.  It  is  not  any  such  imaginary 
theory  that  I  have  now  to  deal  with,  however,  but 
with  opinions  which  have  found  a  place  in  the  works 
of  astronomers  from  whom  I  very  unwillingly  differ. 

I  propose  to  exhibit  the  reasons  which  have  led  me 
to  believe  that,  so  far  from  knowing  the  real  figure  of 
the  sidereal  system,  astronomers  have  not  been  able  to 
penetrate  to  its  limits  in  any  direction ;  that  leading 
stars,  such  as  those  discussed  in  the  preceding  chapter, 
are  distributed  throughout  space  to  the  very  farthest 
limits  and  beyond  the  very  farthest  limits  that  our 
most  powerful  telescopes  can  attain  to  ;  that  the  stars 


MINOR  STARS.  259 

are  arranged  in  groups  and  clustering  aggregations,  in 
streams  and  whorls  and  spirals,  in  a  manner  altogether 
too  complex  for  us  to  hope  to  interpret ;  and  that  in 
these  aggregations  stars  of  all  degrees  of  real  magni- 
tude are  mixed  up,  from  suns  as  large  as  Sirius  down 
to  orbs  which  may  be  smaller  than  any  of  the  primary 
planets  of  the  solar  system. 

Now  let  us  consider  step  by  step  the  evidence  we 
have  on  these  points. 

We  know,  from  the  existence  of  double,  triple,  and 
multiple  stars,  in  which  the  components  are  often 
very  unequal  in  splendor,  that  combinations  of  stars 
exist  in  which  one  or  two  may  be  suns  like  our  own, 
while  the  rest,  or  some  of  the  rest,  are  relatively  mi- 
nute. This,  however,  has  of  course  long  been  known; 
and  it  is  only  as  a  preliminary  step  in  the  investigation 
that  I  here  advance  so  trite  an  instance. 

Next  let  us  consider  such  star-clusters  as  contain 
orbs  of  the  eighth  or  ninth  magnitude,  besides  a  mul- 
titude of  minute  stars.  These  clusters  must  of  course 
be  regarded  as  lying  within  the  sidereal  system,  since 
no  external  galaxies  could  reasonably  be  supposed  to 
contain  orbs  so  infinitely  transcending  even  Sirius  in 
magnitude  as  to  shine  from  beyond  the  enormous  gap 
separating  us  from  such  galaxies  with  a  light  exceed- 
ing that  derived  from  many  stars  within  the  sidereal 
system.  Now,  regarding  these  clusters  as  forming 
part  and  parcel  of  the  sidereal  system,  we  find  in  the 
existence  of  multitudes  of  minute  orbs  within  their 
range  a  proof  that  diversity  of  magnitude  in  schemes 
of  associated  stars  is  to  be  regarded  as  a  feature  of 


26o  OTHER  WORLDS  THAN  OURS. 

certain  parts,  at  any  rate,  of  our  galaxy ;  and  we  shall 
therefore  be  the  less  surprised  if  we  should  find  rea- 
son for  believing  that  it  is  a  characteristic  peculiarity 
of  the  galactic  system. 

Now,  with  regard  to  the  nebulae  (resolvable  and  ir- 
resolvable), and  their  claim  to  be  regarded  as  external 
galaxies,  I  shall  have  much  to  say  farther  on  ;  but  I 
may  remark,  in  passing,  that  we  have  precisely  the 
same  reasons  for  believing  that  many  of  these  objects 
lie  within  the  range  of  the  solar  system  as  have  been 
already  considered  in  the  case  of  star-clusters.  Their 
component  stars,  to  be  visible  at  all,  must  fall  within 
the  range  of  distance  which  astronomers  have  assigned 
to  the  boundaries  of  the  galaxy,  since  some  stars  even 
within  that  range  cease  to  be  separately  visible  in  the 
most  powerful  telescopes  man  has  yet  constructed.  So 
that  when  in  these  objects  we  see  a  few  or  many  dis- 
tinct stars,  and  a  mass  of  nebulous  light  which  we 
judge  to  proceed  from  an  indefinitely  large  number 
of  minute  stars,  we  again  have  very  decided  evidence 
of  the  fact  that  in  one  and  the  same  region  of  the  side- 
real system  there  may  exist  leading  stars  (so  to  speak) 
and  innumerable  stars  relatively  minute. 

"With  considerations  such  as  these  (and  I  might  add 
many  others)  to  guide  us,  let  us  proceed  to  consider 
the  teachings  of  the  Milky  Way  itself,  that  we  may 
see  whether  that  wonderful  zone  indeed  represents,  as 
has  been  thought,  the  sidereal  system  itself,  or  only 
an  aggregation  of  minute  orbs  altogether  insignificant, 
separately,  in  comparison  with  our  sun  or  Sirius, 
Aldebaran  or  Betelgeux,  Yega  or  Arcturus. 


MINOR  STARS.  26i 

The  star-gauging  of  Sir  "W.  Herschel,  interpreted 
according  to  his  hypothesis  of  stellar  distribution, 
pointed  to  an  extension  of  the  Milky  Way  laterally  to 
a  distance  exceeding  some  eighty  times  that  which 
separates  us  from  the  first-magnitude  stars.  So  that, 
regarding  sixth-magnitude  stars  as  on  the  average 
about  ten  times  as  far  from  us  as  those  of  the  first 
magnitude  (the  usual  estimate),  we  see  that  the  outer- 
most parts  of  the  galaxy  must  lie  (according  to  Sir 
W.  Herschel's  theory)  about  eight  times  as  far  from 
us  as  the  sphere  of  the  sixth-magnitude  stars.  Now, 
Sir  John  Herschel  was  led  by  his  observations  of  the 
southern  heavens  to  so  far  modify  his  father's  theory 
as  to  describe  the  Milky  Way  as  probably  shaped  like 
a  flat  ring,  the  stars  down  to  the  tenth  magnitude 
being  in  a  sense  dissociated  from  the  ring,  while  he 
regarded  the  probable  distance  of  the  outermost  limits 
of  the  ring  as  seven  hundred  and  fifty  times  instead 
of  but  eighty  times  the  mean  distance  of  the  first-mag- 
nitude stars.  This  difference  of  opinion,  it  may  be 
remarked,  though  obviously  not  surprising  when  we 
consider  the  enormous  difficulty  of  the  problem  pre- 
sented by  the  sidereal  system,  is  yet  sufficient  to  indi- 
cate the  probability  that  an  important  error  has  been 
made  in  the  hypothesis  which  underlies  the  accepted 
theories  respecting  the  galaxy.  But,  be  this  as  it  may, 
in  regarding  the  Milky  Way  as  shaped  like  a  flat  ring 
(cloven  through  one  half  of  its  circumference)  whose 
medial  section  resembles  generally  the  space  between 
the  dark  concentric  circles  in  the  accompanying  fig- 
ure (in  which  SB  equals  eight  times  SA),  I  have  not 


262 


OTHER   WORLDS  THAN  OURS. 


adopted  a  structure  which  exaggerates  the  difficulties 
presented  by  the  disk  or  ring  theory  of  the  Milky  "Way. 


FIG.  2.— The  Galactic  Cloven  Flat  Eing  (plan). 

The  cross-section  would  be  somewhat  as  shown  in 
Fig.  3. 

Now,  accepting  this  modified  figure,  as  better  ac- 
cording with  the  results  of  star-gauging  than  Sir  "W. 


FIG.  3. — The  Galactic  Cloven  Flat  Eing  (section). 

Herschel's  theory  that  the  Milky  Way  forms  a  cloven 
disk,  let  us  consider  whether  any  peculiarities  of  the 


MINOR  STARS.  263 

Milky  Way  seem  to  oppose  themselves  to  this  inter- 
pretation of  its  structure. 

In  the  first  place,  then,  there  is  a  gap  or  rift  ex- 
tending right  across  the  single  part  of  the  Milky  Way 
in  the  constellation  Argo  ;  so  that  we  must  conceive 
that  from  S  toward  1,  in  Fig.  2,  the  flat  ring  is  broken 
through  by  some  such  rift  as  is  indicated  by  the  broken 
lines  in  that  direction.  Next  there  is,  in  the  constella- 
tion Crux,  a  pear-shaped  vacuity  of  considerable  size, 
and  bounded  by  well-defined  edges ;  so  that  we  must 
conceive  that  from  S  toward  2  (Fig.  2)  the  flat  ring 
is  tunnelled  through  by  some  such  passage  as  is  indi- 
cated by  the  dotted  lines  in  that  direction.  A  similar 
tunnelling,  but  of  different  cross-section,  must  exist  in 
direction  S  3  (as  shown  by  the  dotted  lines)  to  account 
for  the  dark  gap  in  the  constellation  Cygnus.  Next, 
where  the  Milky  Way  is  double,  a  large  portion  of  one 
branch  is  discontinuous,  so  that  the  upper  part  of  the 
double  portion  of  the  ring  in  Fig.  2  must  be  supposed 
removed  between  the  broken  lines  from  S  to  4  and  5. 
Over  the  so-called  double  stream  there  are  in  places 
strange  convolutions,  in  others  numerous  branching 
and  interlacing  streams,  whose  complexity  indeed  de- 
fies description  ;  so  that  the  portion  3  B  2  of  the  ring 
must  be  supposed  corrugated  in  the  strangest  way, 
and  further  to  throw  out  plane  and  curved  sheets  of 
stars  presented  tangentially  toward  S.  Lastly,  the 
single  portion  of  the  Milky  Way  is  very  faint  indeed 
toward  6,  so  that  here  we  must  conceive  its  figure 
trenched  in  upon  in  the  way  indicated  by  the  dot-and 
peck  line. 


264  OTHER    WORLDS  THAN  OURS. 

Thus,  even  without  considering  a  multitude  of  mi- 
nuter peculiarities  of  structure,  we  are  led  to  the  con- 
clusion that  the  Milky  Way,  judged  according  to  the 


FIG.  4. — The  Galactic  Flat  Ring,  modified  in  accordance  with  the 
observed  peculiarities  of  the  Milky  Way. 


fundamental  hypothesis  of  Sir  "W.  Herschel,  has  some 
such  shape  as  I  have  endeavored  to  exhibit  in  the  ac- 
companying figure.  Although  I  have  not  indicated 
here  the  corrugations  of  the  ring,  nor  a  tithe  of  the 
various  overlapping  layers  which  would  be  required  to 
account  for  the  appearance  of  the  Milky  Way  between 
Centaurus  and  Ophiuchus,  yet  the  deduced  figure  is 
by  no  means  inviting  in  its  simplicity.  It  is,  however, 
absolutely  certain  that  the  sidereal  system,  as  far  as  its 
more  densely  aggregated  star-regions  are  concerned, 
has  some  such  figure  as  this,  if  we  are  to  accept  the 
principle  of  Sir  W.  Herschel's  star-gaugings. 

Now,  in  turning  our  thoughts  to  the  recognition  of 
a  more  simple  explanation  of  observed  appearances,  it 
will  be  well  that  we  should  consider  some  peculiarities 


MINOR  STARS. 


265 


of  tlie  Milky  Way  which  we  have  not  yet  attended  to. 
In  the  first  place,  I  would  invite  attention  to  a  pecu- 
liarity observed  by  Sir  John  Herschel  in  different 
parts  of  the  galaxy — the  fact,  namely,  that  in  places 
the  edge  of  the  Milky  Way  is  quite  sharply  defined. 
One  half  of  a  telescopic  field  of  view  may  be  quite 
clear  of  stars,  or  show  only  a  few  straggling  orbs,  while 
the  other  half  presents  what  has  been  called  a  "  Milky 
Way  field  " — that  is,  a  region  profusely  sprinkled  with 
stars,  the  boundary  between  the  two  portions  being 
well  defined.  When  we  see  that  a  cluster  of  objects 
presents  a  well-defined  edge,  what  conclusion  do  we 
draw  as  to  the  position  of  the  object  ?  Is  it  not  in 
such  a  case  absolutely  certain  that  the  distance  of  the 
cluster  enormously  exceeds  the  distance  between  its 
component  parts  — or,  in  other  words,  that  the  observer 
is  far  outside  the  cluster?  Many  instances  will  at 
once  suggest  themselves  to  the  reader  in  illustration 
of  this  remark. 

We  conclude,  then,  that  these  portions  of  the  Milky 
Way,  at  any  rate,  whether  they  be  regarded  as  projec- 
tions or  nodules,  are  definite  clustering  aggregations 
very  far  removed  from  us.  Other  parts  of  the  Milky 
Way  may  also  be  removed  bodily,  so  to  speak,  to 
enormous  distances,  because  a  cluster  which  has  not 
a  definite  edge  may  be  as  far  removed  as  one  which 
has ;  but  certainly  those  portions  are. 

!N^ext  let  us  consider  what  opinion  we  may  found 

on  the  existence  of  dark  regions  in  the  Milky  Way ; 

and  here  I  refer  not  merely  to  such  large  and  obvious 

vacuities  as  the  coal-sack  in  Crux  or  the  oval  opening 

12 


266  OTHER    WORLDS  THAN  OURS. 

in  Cygnus,  but  also  to  small  openings,  in  winch,  though 
they  occur  even  in  rich  regions  of  the  Milky  Way, 
there  is  not,  according  to  Sir  W.  Herschel's  descrip- 
tion, even  a  telescopic  star  to  be  seen. 

Judged  apart  from  preconceived  opinions,  such 
openings  as  these,  according  to  all  laws  of  probability, 
indicate  that  the  portion  of  the  Milky  Way  in  which 
they  occur  has  not  a  very  great  lateral  extension.  To 
return  for  a  moment  to  Fig.  2,  it  will  be  seen  at  once 
that  an  aperture  extending  laterally  through  a  star- 
system  so  shaped  must  have  a  particular  direction  and 
be  perfectly  straight  in  order  to  be  visible  to  observers 
placed,  as  we  are  supposed  to  be,  in  the  central  open- 
ing. It  is  altogether  improbable  that  one  such  open- 
ing should  exist  by  accident,  and  absolutely  impos- 
sible that  many  should.*  We  are  forced  therefore  to 
infer  that,  instead  of  the  enormous  lateral  extension 
assigned  to  the  Milky  Way,  the  galaxy  has  in  these 
places  certainly,  and  elsewhere  probably,  a  lateral  ex- 
tension not  greatly  exceeding  its  depth. 

It  is  further  to  be  noted  that  the  lucid  stars  over 
that  zone  of  the  heavens  which  is  occupied  by  the 
galaxy  show  a  very  decided  preference  for  the  parts 
of  that  zone  which  are  actually  traversed  by  the  Milky 
Way.  For  instance,  we  find  no  stars  above  the  fifth 
magnitude,  and  very  few  of  these,  in  the  Coal-sacks,  or 

*  Sir  John  Herschel  has  distinctly  indicated  this  inference,  as  he  has 
many  other  matters  which  make  strongly  against  the  received  theory  of 
the  sidereal  system.  Nor  is  he  unconscious  of  their  bearing.  Appar- 
ently unwilling  at  present  to  press  them  to  their  full  extent,  he  is  com- 
monly satisfied  by  noting  that  they  do  not  seem  to  accord  with  views  he 
baa  elsewhere  dwelt  upon. 


MINOR  STARS. 


267 


m  the  rift  which  crosses  the  Milky  "Way  in  Argo,  or, 
again,  in  the  space  which  lies  between  the  two  branches 
where  the  Milky  "Way  is  double.  If  this  is  an  accident, 
it  is  a  yery  extraordinary  one,  especially  when  it  is  re- 
membered that  the  region  where  it  occurs  is  the  very 
part  of  the  heavens  where  stars  of  all  magnitudes  may 
be  expected  to  be  most  profusely  distributed ;  that  the 
spaces  thus  left  vacant  form  no  inconsiderable  aliquot 
part  of  that  zone ;  and  that,  according  to  the  accepted 
theory,  there  is  no  reason  for  expecting  any  peculiarity 
of  the  sort. 

Thus,  again,  setting  aside  preconceived  opinions, 
and  judging  only  according  to  the  evidence,  we  seem 
led  to  regard  the  coincidence  as  not  accidental,  but  as 
indicating  that  there  really  is  a  very  close  association 
between  the  bright  stars  and  those  small  stars  form- 
ing the  milky  light,  which,  according  to  the  accepted 
theory,  would  lie  so  many  times  farther  from  us.* 

Now,  if  we  have  not  been  mistaken  so  far,  it  is  very 
clear  what  views  we  are  to  form.  If  the  Milky  "Way 
is  to  be,  first,  a  clustering  aggregation  separated  from 
us  by  an  interval  comparatively  clear  of  small  stars ; 
secondly r,  so  shaped  that  the  cross-section  of  the  stream 
is  everywhere  not  far  from  a  roughly  circular  figure ; 
and,  thirdly,  associated  very  closely  with  the  bright 
stars  seen  in  the  same  field  of  view,  then  must  its 

*  I  may  add  that,  in  drawing  the  maps  for  my  new  star-atlas,  I  have 
been  very  much  surprised  to  find  how  in  many  cases  the  position,  nay 
the  very  shape,  of  the  Milky  Way  is  indicated  by  the  lucid  stars  which 
fall  on  its  zone.  Although  my  own  views  had  led  me  to  look  for  a  pe- 
culiarity of  the  sort,  it  has  been  much  more  striking  in  its  character  than 
I  had  expected. 


268  OTHER   WORLDS  THAN  OURS. 

structure  be  somewhat  as  shown  in  Fig.  5,  in  which 
the  disks  represent  lucid  stars  (very  much  exagger- 
ated of  course  in  size),  while  the  fine  dotting  represents 


FIG.  5.— The  Milky  Way  regarded  as  a  Spiral. 

the  spiral  of  relatively  minute  stars,  clustering  along 
the  spiral  group  of  leading  stars.  It  will  be  seen  at 
once  how,  to  an  observer  placed  at  S,  the  various  fea- 
tures of  the  Milky  Way  can  be  accounted  for  by  this 
figure.  Toward  a  would  lie  the  gap  in  Argo  ;  toward 
"b  two  branches,  one  faint,  and  in  part  evanescent 
through  enormity  of  distance,  the  other  forming  the 
brightest  part  of  the  spiral ;  toward  d  the  projection  in 
Cepheus ;  toward  e  the  faint  part  of  the  Milky  Way  in 
Gemini  and  Monoceros.  The  Coal-sacks  would  be 
simply  accounted  for  by  conceiving  that  branches  seen 
toward  the  same  general  direction,  but  at  different 
distances,  do  not  lie  in  the  same  general  plane,  and  so 
may  appear  to  interlace  upon  the  heavens.  We  are 
not  only  justified  in  supposing  this,  but  forced  to  do 


MINOR  STARS. 


269 


BO  by  the  way  in  which  the  stream  of  milky  light  is 
observed  to  meander  on  its  course-  athwart  the  heavens. 
The  branching  extensions  serve  very  well  to  account 
for  the  appearance  of  the  Milky  Way  between  Centau- 
rus  and  Ophiuchus,  where  the  interlacing  branches  and 
the  strange  convolutions  and  clustering  aggregations 
described  by  Sir  John  Herschel  are  chiefly  gathered. 

I  would  not  have  it  understood,  however,-  that  I  at 
all  insist  on  the  general  shape  of  the  spiral  shown  in 
Fig.  5.  On  the  contrary,  that  curve  is  only  one  out  of 
several  which  might  fairly  account  for  the  observed 
appearance  of  the  Milky  Way ;  and  I  have  often  felt 
inclined  to  doubt  whether  a  single  spiral  of  this  sort 
be  in  reality  the  best  way  of  accounting  for  the  ob- 
served appearance  of  the  galactic  zone.  What  I  do 
insist  upon  as  most  obviously  forced  upon  us  by  the 
evidence  is,  that  (1)  the  apparent  streams  formed  by 
the  Milky  Way  upon  the  heavens  indicate  the  exist- 
ence of  real  streams  in  space ;  and  (2)  that  the  lucid 
stars  seen  on  the  stream  are  really  associated  with  the 
telescopic  stars  which  form,  so  to  speak,  the  body  of 
the  stream.  Whether  that  stream  form  a  single  spiral 
or  several,  or  whether,  instead  of  spirals,  there  may  not 
l)e  a,  number  of  dosed  rings  of  small  stars,  placed  at 
different  distances  from  us,  and  lying  in  all  directions 
round  the  medial  plane  of  the  galaxy,  l>ut  m*ore  or  less 
tilted  to  that  plane  (the  sun  not  lying  within  any  one 
of  the  rings],  are  questions  which  can  only  be  resolved 
by  the  systematic  scrutiny  of  this  wonderful  zone. 

The  chief  points  to  be  noticed  among  the  considera- 
tions flowing  from  these  general  views  are  these : 


Z7Q 


OTHER    WORLDS  THAN  OURS. 


In  the  first  place,  the  only  marked  difference  be- 
tween the  stars  of  the  leading  magnitudes  (say  the 
first  ten)  lying  in  the  galactic  zone,  and  those  lying 
without  it,  consists  in  the  fact  that  the  former  are  as- 
sociated with  countless  multitudes  of  smaller  stars, 
while  the  latter  appear  not  to  have  such  attendants,  or 
not  so  many  of  them.  We  shall  see  presently  that  the 
extra-galactic  stars  are  associated,  and  in  a  very  in- 
timate manner,  with  groups  of  very  minute  stars — of 
stars  so  minute  indeed  as  not  to  be  separately  discern- 
ible— so  that  astronomers  have  been  led  to  regard  such 
groups  as  external  galaxies.  But,  except  in  one  region, 
we  do  not  find  outside  the  galactic  zone  any  appear- 
ances reminding  us  of  the  aspect  of  the  Milky  "Way 
itself.  In  that  region  lie  the  two  Magellanic  Clouds, 
resembling  the  Milky  Way  in  their  general  appearance, 
but  seen  when  placed  under  telescopic  scrutiny  to  differ 
from  it  in  this,  that  among  the  minute  stars  which 
cause  the  milky  light  are  numbers  of  nebulae,  of  classes 
not  found  commonly,  if  at  all,  in  the  galactic  zone. 

In  the  second  place,  we  must  conclude  that  un- 
counted millions  of  stars  exist  which  are  very  minute 
indeed  in  comparison  with  those  which  we  have  been 
led  to  regard  as  suns.  That  these  relatively  minute 
orbs  may  be  absolutely  large — far  larger,  for  instance, 
than  our  own  earth — may  indeed  be  accepted  as  cer- 
tain. But  it  is  difficult  to  believe  that  they  subserve 
purposes  similar  to  those  of  our  own  sun.  One  cannot 
but  see  that  orbs  such  as  these  would  not  have  that 
permanence  of  character,  as  sources  of  heat-supply, 
which  would  seem  to  be  necessary  in  the  case  of  a  real 


MINOR  STARS.  271 

gun.  We  know,  indeed,  that  among  the  small  stars 
of  the  Milky  Way  there  is  a  proneness  to  irregular 
variation  which  is  not  recognized,  or  is  altogether  ex- 
ceptional, among  the  lucid  stars.  In  the  neighbor- 
hood of  the  Milky  Way,  with  scarcely  an  exception, 
those  temporary  stars  have  blazed  out  which  have 
formed  a  subject  of  such  perplexity  to  the  thoughtful 
astronomer.  Under  what  conditions  the  small  orbs  in 
the  Milky  Way  actually  exist,  whether  clusters  of  them 
will  eventually  segregate  from  their  neighbors  to  form 
suns,  or  whether,  after  long  voyaging  in  spiral  and  con- 
torted paths  under  the  varying  influences  of  the  attrac- 
tions of  leading  stars,  these  minute  orbs  will,  for  the 
most  part,  be  forced  to  settle  down  as  attendants  round 
the  major  ones,  it  is  as  yet  altogether  impossible  to 
judge.  It  may  be  that  they  bear  the  same  sort  of  re- 
lation to  the  leading  stars  that  certain  cometic  and 
metoric  families,  referred  to  in  Chapter  IX.,  bear  to 
the  major  planets  of  the  solar  system,  not  being  in  any 
case  absolutely  dependent  on  any  large  star,  but  yet 
returning  in  cycles  which  must  be  measured  by  mill- 
ions of  eons,  to  temporary  dependence  on  one  sun 
after  another,  until  in  the  course  of  time,  under  the 
action  of  processes  somewhat  resembling  those  I  have 
conceived  to  take  place  in  the  formation  of  the  solar 
system,  the  conditions  under  which  they  move  will 
have  become  so  far  altered  as  to  lead  to  the  breaking 
up  of  the  Milky  Way  into  distinct  systems.  Indeed, 
as  Sir  William  Herschel  was  led  by  other  considera- 
tions long  since  to  point  out,  there  are  signs  in  parts 
of  the  Milky  Way  which  would  seem  to  indicate  that 


272  OTHER   WORLDS  THAN  OURS. 

several  such  systems  have  already  reached  an  advanced 
stage  of  development. 

But  perhaps  the  most  important  conclusion  de- 
ducible  from  the  circumstances  I  have  dwelt  upon 
(assuming  my  interpretation  of  them  to  be  in  the  main 
correct)  is  this,  that  we  can  no  longer  suppose  we  have 
in  any  direction  pierced  to  the  limits  of  the  sidereal 
system.  So  long  as  a  general  approach  to  uniformity 
of  distribution  was  understood  to  prevail  within  that 
system,  there  was  a  ready  means  of  determining  when 
the  telescopist  had  reached  in  any  given  direction  the 
limits  of  the  system.  To  use  the  words  of  Prof. 
Nichol,  "  "WTien  an  eye  is  directed  toward  a  prolonged 
bed  of  stars,  there  is  no  reason  to  fancy  that  it  has 
reached  the  termination  of  that  stratum  so  long  as 
there  appears,  behind  the  luminaries  which  are  indi- 
vidually seen,  any  milky  or  nebulous  light ;  such  light 
probably  arising  always  from  the  blended  rays  of  re- 
moter masses.  But,  if,  after  struggling  long  with  a 
nebulous  ground,  we  obtain  a  telescope  that  gives  ua 
additional  light  with  a  perfectly  lilack  sky,  we  then 
have  every  reason  the  circumstances  can  furnish  on  be- 
half of  the  supposition  that  at  length  we  have  pierced 
through  the  stratum,  a  probability,  indeed,  which  can 
be  converted  into  certainty  in  only  one  way — viz., 
when  no  increase  of  orbs  follows  on  the  application  of 
a  still  larger  instrument."  Sir  John  Herschel  has  ex- 
pressed a  similar  view,  and  there  can,  indeed,  be  no 
doubt  that,  adopting  the  fundamental  hypothesis  on 
which  .accepted  views  are  founded,  the  test  above  de- 
scribed is  an  absolutely  certain  one. 


MINOR  STARS.  2^ 

But,  if,  instead  of  penetrating  farther  and  farther 
into  space  when  "struggling  long  with  a  nebulous 
ground  "  (to  use  Prof.  Nichol's  striking  but  somewhat 
incorrect  expression),  we  have  in  reality  only  been 
searching  with  more  and  more  minuteness  within  a 
definite  cluster  or  stream  of  stars,  we  can  no  longer 
come  to  the  conclusion  he  has  insisted  upon.  We 
have  reached  the  limits  of  minuteness  which  the  stars 
of  the  cluster  or  stream  attain  to  ;  we  have  learned  per- 
haps all  that  we  can  learn  about  that  cluster  or  stream ; 
but  we  can  no  more  be  said  to  have  reached  the  limits 
of  the  sidereal  system  in  that  direction  than  we  can 
be  said  to  have  reached  the  outermost  bounds  of  the 
universe  in  the  direction  of  the  cluster  in  Hercules, 
when  that  magnificent  object  has  been  thoroughly  re- 
solved with  the  telescope. 

Here,  then,  if  I  have  seemed  to  narrow  the  limits 
of  the  sidereal  scheme  by  bringing  the  star-myriads 
of  the  Milky  "Way,  which  had  been  regarded  as  many 
times  farther  from  us  than  the  lucid  stars,  into  direct 
association  with  these  luminaries,  I  make  amends  by 
pointing  out  that  in  all  probability  the  limits  of  the 
sidereal  system  lie  far  beyond  the  range  of  the  most 
powerful  telescopes  man  has  yet  constructed.  In  fact, 
there  is  here  a  somewhat  singular  interchange  of  po- 
sition between  the  new  and  the  accepted  theories. 
According  to  the  views  usually  accepted,  the  small 
stars  in  the  Milky  "Way  are  really  as  large,  on  the  av- 
erage, as  the  lucid  stars,  whereas,  according  to  my 
views,  they  are  relatively  minute.  But,  according  to 
the  accepted  theories,  the  scattered  stars  of  very  low 


174  OTHER   WORLDS  THAN  OURS. 

magnitudes  in  the  extra-galactic  heavens  must  be  re- 
garded as  relatively  minute,  since  it  has  been  rendered 
certain,  according  to  those  theories,  that  the  limits  of 
the  sidereal  system  are  relatively  close  in  this  direc- 
tion, and  we  cannot  suppose  these  stars  to  lie  beyond 
those  limits  (as  they  must  do,  if  really  large).  Now, 
according  to  my  views,  there  is  nothing  to  prevent 
these  minute  stars  from  including  among  their  num- 
ber orbs  as  vast  as  Sirius,  or  many  times  vaster. 
]STay,  even  within  the  galactic  zone  itself  there  are 
stars  to  which  my  theory  gives  as  noble  proportions  as 
the  accepted  views.  For,  in  the  southern  Coal-sack, 
there  are  minute  telescopic  stars,  as  Sir  John  Herschel 
tells  us,  and  these  orbs,  according  to  the  accepted 
views,  must  be  regarded  as  belonging  to  the  galactic 
circle,  though  inexplicably  segregated  from  their  fel- 
lows. According  to  the  views  I  have  been  led  to 
form,  many  of  these  telescopic  stars  must  be  regarded 
as  suns  lying  far  beyond  the  galactic  spiral,  or  perhaps 
associated  with  outer  whorls  of  this  spiral  which  no 
telescope  made  by  man  can  ever  reveal  to  us. 

And  this  leads  me  to  consider  two  phenomena 
which  are  altogether  inexplicable,  I  conceive,  on  any 
theory  except  mine. 

The  first  is  the  existence  of  excessively  faint 
streams  of  light — star-streams  doubtless,  though  the 
components  are  not  separately  visible — in  certain  re- 
gions of  the  heavens.  Sir  John  Herschel,  who  de- 
tected this  strange  phenomenon,  speaks  of  the  streams 
as  so  very  faint  that  the  idea  of  illusion  has  contin- 
ually arisen  subsequently ;  yet  he  dwells  far  too 


MINOR  STARS.  275 

clearly  on  the  characteristics  of  the  phenomenon  for 
any  doubt  to  remain  as  to  its  reality.  The  faintest 
possible  stippling  of  the  field  of  view — the  minute 
points  of  light  being  obviously  there,  though  it  was  im- 
possible to  see  them  individually — a  mottling  which 
moved  with  the  stars  as  he  moved  the  tube  to  and  fro, 
such  are  the  terms  in  which  Sir  John  Herschel  speaks 
of  this  interesting  phenomenon. 

Now,  no  doubt  whatever  can  exist  that,  if  these 
faint  streams  really  belong  to  the  sidereal  system,  they 
are  left  altogether  unaccounted  for  by  the  ordinary 
views  respecting  the  structure  of  that  system.  There 
is  no  continuity  between  the  stars  composing  them 
and  even  the  minutest  telescopic  stars  visible  in  the 
same  general  direction  ;  so  that  a  vast  void  must  sepa- 
rate them  from  the  outermost  of  those  telescopic  stars. 
According  to  my  theory,  they  simply  belong  to  out- 
lying whorls  of  the  spiral  galaxy,  and  the  telescopic 
stars  seen  upon  them  bear  the  same  relation  to  them 
that  the  lucid  stars  bear  to  the  Milky  Way. 

The  second  point  is  perhaps  even  more  striking. 
In  certain  directions  Sir  John  Herschel  recognized  the 
existence  of  two  or  more  distinctly-marked  classes  of 
stars,  as  though,  he  says,  definite  sets  of  stars,  sepa- 
rated by  comparatively  void  intervals,  lay  in  those 
directions.  It  is  clear  that  this  association  of  the 
stars  into  sets  is  as  distinctly  opposed  to  the  views 
ordinarily  accepted  as  it  is  obviously  an  arrangement 
to  be  expected  according  to  my  theory  of  the  constitu- 
tion of  the  sidereal  system. 

Quite  early  in  my  consideration  of  the  subject  I  am 


t?6  OTHER   WORLDS  THAN  OURS. 

now  upon,  the  idea  suggested  itself  to  me  that  in  the 
proper  motions  of  the  stars  we  have  a  means  of  form- 
ing an  estimate  of  the  distances  of  these  orbs ;  and, 
further,  of  detecting  any  laws  associating  them  to- 
gether, whether  into  streams  or  clusters ;  and  that  the 
evidence  thus  obtained  was  likely  to  be  in  many  re- 
spects more  trustworthy  than  that  afforded  by  the 
apparent  magnitudes  of  the  stars.  Two  processes  of 
inquiry  suggested  themselves.  The  first  consisted  in 
a  careful  comparison  of  the  mean  motions  of  stars  of 
different  apparent  size,  in  order  to  determine  whether, 
on  the  average,  small  stars  are  so  far  off  that  we  can 
look  upon  them  as  in  reality  no  smaller  on  the  average 
than  those  which  appear  larger.  The  second  consist- 
ed in  charting  down  the  proper  motions,  so  as  to  de- 
tect any  signs  of  star-drift  which  might  haply  appear 
in  different  parts  of  the  heavens.  I  confess  that  I  had 
not  by  any  means  expected  results  so  strikingly  con- 
firmatory of  my  views  as  those  I  actually  obtained. 

The  first  method  of  inquiry,  instead  of  giving  an 
average  amount  of  proper  motion  to  the  smaller  stars 
somewhat,  or  perhaps  even  considerably,  greater  than 
was  to  be  expected,  according  to  the  theory  which  sets 
these  stars  at  an  enormous  distance,  actually  gave 
them  a  mean  motion  equal  to  that  of  stars  of  the  first 
three  magnitudes.  It  became  evident,  then,  that  not 
only  are  small  stars  (I  am  here  speaking  of  stars  visi- 
ble to  the  naked  eye)  mixed  up  as  I  had  thought  with 
bright  stars  visible  in  the  same  general  direction,  but 
that  distance  is  less  available  to  explain  the  smallness 
of  the  stars  even  than  I  had  supposed.  I  had  thought 


MINOR  STARS.  277 

that  certainly  a  large  proportion  of  the  small  stars 
must  in  reality  be  very  far  from  us ;  but  it  appeared 
that  the  proportion  of  stars  whose  smallness  is  so  to  be 
accounted  for  is  in  reality  exceedingly  minute.  There 
must  therefore  be  myriads  of  really  small  stars  for 
every  leading  orb. 

The  second  method  of  research  led  to  the  strange 
result  that  in  many  parts  of  the  heavens  a  community 
of  motion  can  be  recognized,  among  star-groups  far 
larger  in  extent  than  I  had  expected  to  find  thus  drift- 
ing through  space.  Knowing  that,  whatever  view  we 
form  of  the  sidereal  universe,  we  must  yet  recognize 
the  fact  that  in  every  direction  stars  at  very  different 
distances  must  be  visible,  I  had  not  hoped  to  find  over 
any  large  region  of  space  the  traces  of  a  community 
of  motion.  Nor  even  in  small  regions  had  I  hoped  to 
recognize  very  decided  traces  of  star-drift,  because  I 
was  conscious  that,  even  with  three  or  four  stars  really 
forming  a  drifting  group,  there  would  nearly  always 
be  found  three  or  four  others,  either  much  farther  off 
or  much  nearer,  and  altogether  dissociated  from  the 
drifting  set.  Indeed,  I  imagined,  when  I  began  the 
inquiry,  that  the  most  remarkable  instance  of  star- 
drift  in  the  heavens  was  that  detected  (though  dif- 
ferently explained)  by  Baron  Madler  in  the  constella- 
tion Taurus. 

I  found,  however,  that  in  other  regions,  a  far  more 
obvious  tendency  to  drift  can  be  recognized.  Perhaps 
the  most  remarkable  instance  of  all  is  that  illustrated 
in  the  accompanying  plate.  This  picture  represents 
the  motions  in  the  constellations  Cancer  and  Gemini. 


278  OTHER   WORLDS  THAN  OURS. 


It  will  be  noticed  that  tliougli  here  and  there  stars  ap- 
parently not  belonging  to  the  system  appear  in  the 
same  range  of  view,  yet  the  star-drift  is  unmistakable. 
The  general  parallelism  of  motion  is  very  striking; 
and  the  difference  in  the  amount  of  motion  observed 
in  different  stars  is  only  what  was  to  be  expected  in  a 
star-group  whose  range  in  distance,  if  equivalent  to  its 


MINOR  STARS.  279 

lateral  extent,  must  be  such  as  fully  to  account  for  the 
range  in  the  amount  of  apparent  motion. 

Fig.  6  exhibits  one  out  of  many  parts  of  the  heav- 
ens in  which  different  sets  of  stars  are  observed  to  be 
drifting  in  different  ways. 

It  will  be  seen  that  here  there  are  three  sets — those 
included  in  the  space  #,  those  in  space  5,  and  those 
left  unenclosed,  which  are  very  obviously  drifting, 


£ 

t    - 


Fio.  6. — Observed  Proper  Motions  of  Stars  in  Ursa  Major  and 
Neighborhood. 

each  in  its  special  direction.  The  stars  within  the 
space  ~b  are  &  y,  B,  e,  and  £,  of  the  Greater  Bear,  with 
three  smaller  stars.  Their  drift  is,  I  think,  most  sig- 
nificant. If  in  truth  the  parallelism  and  equality  of 


28o  OTHER   WORLDS  THAN  OURS. 

motion  are  to  be  regarded  as  accidental,  the  coinci- 
dence is  one  of  a  most  remarkable  character.  But 
such  an  interpretation  can  hardly  be  looked  upon  as 
admissible,  when  we  remember  that  the  peculiarity  is 
only  one  of  a  series  of  instances,  some  of  which  are 
scarcely  less  striking.  One  of  these  is  presented  in 
the  accompanying  figure  in  which  the  proper  motions 
in  the  stars  a,  &  and  y,  Arietis,  and  four  other  stars 
in  the  neighborhood,  are  exhibited.*' 

Here  /3  and  7  may  be  regarded  as  drifting  with  a, 
but  having  a  motion  of  their  own  in  addition,  suffi- 
cing to  account  for  the  want  of  strict  parallelism  be- 
tween their  apparent  motion  and  that  of  a.  The 
other  stars  seem  obviously  to  belong  to  the  same  sys- 


V 

* 


YIQ.  7. — Observed  Proper  Motions  of  Stars  in  Head  of  Aries. 

I  am  led,  by  the  facts  which  have  here  been  briefly 
considered,  rather  to  urge  those  who  have  time  and 
inclination  to  inquire  carefully  into  the  minuter  de- 
tails of  the  sidereal  heavens  than  to  insist  on  any 

*  In  all  these  figures  the  proper  motion  indicated  by  the  length  of 
the  arrow  attached  to  a  star  corresponds  to  the  star's  motion  in  thirty- 
six  thousand  years. 


MINOR  STARS.  281 

views  of  my  own.  While  I  recognize  the  wisdom  and 
necessity  of  that  course  which  the  Herschels  adopted 
in  taking  a  wide  view  of  the  sidereal  system,  and  in 
dealing  rather  with  general  results  than  with  special 
peculiarities,  I  think  the  time  has  come  when  another 
course  is  possible  and  advisable.  The  Herschels  hav- 
ing surveyed  the  field  of  heaven,  it  behooves  us  now 
to  go  over  it  with  a  close  and  searching  scrutiny.  To 
consider  averages  now  is  to  level  the  scarcely  percep- 
tible undulations  in  our  field  of  research,  as  well  as  its 
better-marked  ridges  or  depressions ;  whereas  we  re- 
quire, on  the  contrary,  to  exaggerate  the  variations  of 
level,  so  that  we  may  determine  with  more  certainty 
what  are  the  peculiarities  presented  by  that  most  in- 
teresting field  to  man's  contemplation.  Or,  to  change 
the  illustration,  and  to  quote  the  words  of  the  greatest 
living  master  of  that  kind  of  research  which  I  have 
been  advocating,  "We  must  not  be  deterred  from 
dwelling  consecutively  and  closely  on  these  specula- 
tive views  by  any  idea  of  their  hopelessness  which  the 
objectors  against  ' paper  astronomy'  may  entertain, 
or  by  the  real  slenderness  of  the  material  threads  out 
of  which  any  connected  theory  of  the  universe  has  (at 
present)  to  be  woven.  l  Hypotheses  jingo '  in  this 
stage  of  our  knowledge  is  quite  as  good  a  motto  as 
Newton's  iNon  jingo ' — provided  always  they  be  not 
hypotheses  as  to  modes  of  physical  action  for  which 
experience  gives  no  warrant."  * 

*  From  a  letter  addressed  by  Sir  J.  Herschel  to  the  present  writer 
August  1,  1869. 


CHAPTER  XII. 

THE  NEBULA  :  ARE  THEY  EXTERNAL  GALAXIES  ? 

IN  the  last  chapter  I  have  indicated  reasons  for 
believing  that  the  sidereal  system  extends  far  beyond 
the  range  of  the  most  powerful  telescopes  man  has  yet 
been  able  to  construct.  It  need  hardly  be  said  that, 
supposing  this  view  to  be  correct,  we  cannot  possibly 
see  any  external  galaxies,  unless  they  surpass  our  own 
many  thousands  of  times  in  richness  and  splendor. 
Every  analogy  that  we  have  for  our  guidance  points 
to  the  conclusion  that,  if  our  galaxy  have  limits,  and 
there  exist  in  space  other  galaxies,  then  those  outer 
systems  must  be  separated  from  ours  by  spaces  ex- 
ceeding the  dimensions  of  the  several  galaxies  many 
thousand  or  many  million  fold  in  extent.  We  know 
that  the  distances  separating  the  satellites  from  their 
primaries  exceed  in  an  enormous  ratio  the  dimensions 
of  the  satellites.  The  distances  separating  the  planets 
from  each  other  exceed  in  an  enormous  ratio  the  di- 
mensions of  the  planets.  The  distances  separating 
our  solar  system  from  others  enormously  exceed  the 
dimensions  of  the  various  solar  systems.  And  we  may 
conclude  that  in  all  probability  the  distances  separat- 


THE  NEBULAE.  283 

ing  our  sidereal  system  from  other  similar  systems  in 
space  must  exceed  in  an  enormous  ratio  the  dimen- 
sions of  our  galaxy,  and  of  all  other  such  systems. 

That  the  sidereal  system  has  limits  I  do  not  doubt. 
Of  course  it  may  be  coextensive  with  space  that  is 
absolutely  infinite  in  extent ;  but  we  have  no  reason 
for  believing  that,  in  rising  step  by  step,  from  system 
to  system,  until  we  have  reached  the  highest  class  of 
system  known  to  us,  we  have  reached  the  real  summit 
of  that  perhaps  altogether  limitless  range  of  steps. 
We  know,  indeed,  that  if  light  do  not  suffer  extinction 
in  traversing  space  (and  we  have  as  yet  no  evidence 
that  it  does),  the  extent  of  the  sidereal  system  must  be 
limited,  since  otherwise  the  whole  of  the  starlit  sky 
should  shine  with  the  brilliancy  of  sunlight.*  And  we 

*  This  is,  perhaps,  obvious  ;  but,  if  not,  the  following  proof  may  be 
accepted :  Let  the  whole  of  space  be  conceived  divided  into  spherical 
shells,  having  our  earth  at  their  centre,  the  thickness  of  each  shell  being 
T.  Then  taking  two  shells,  one  at  a  distance  r,  the  other  at  a  distance 
r'  (both  r  and  r'  much  greater  than  T),  we  see  that  the  number  of  stars 
in  these  shells  will  be  proportional  to  r2  T  and  r'!  r  respectively;  that  is, 
will  be  independent  of  the  thickness  of  the  shell  and  vary  as  the  square 
of  its  radius.  (Here  I  am  not  concerned  with  those  departures  from  uni- 
formity which  I  have  considered  in  the  last  chapter,  because  I  suppose 
each  shell  large  enough  to  include  within  it  all  varieties  of  distribution 
and  aggregation.  This  applies,  also,  to  what  follows.)  Now,  the  average 
apparent  size  of  the  stars  of  one  shell  will  be  to  the  average  apparent 
size  of  stars  in  the  other  in  the  inverse  proportion  of  the  respective 
radii  of  the  shells,  the  intrinsic  brightness  of  the  light  received  from  the 
Btars  of  each  set  being  equal.  Thus  the  total  amount  of  light  from  the 
•tars  of  one  shell  is  to  the  total  amount  of  light  from  stars  in  the  other, 

&s  rt  r  x  _L .  r'i  T  x  _— i  :  i.     Hence,  supposing  the  amount  of  light 

received  from  one  shell  to  be  |th  part  of  that  which  would  be  received 
if  the  whole  celestial  sphere  were  as  bright  as  the  sun's,  that  is  as  a 


i84  OTHER    WORLDS  THAN  OURS. 

may  carry  this  argument  even  further.  For,  though 
the  sidereal  system  should  be  limited,  but  other  sys- 
tems similar  to  it  spread  throughout  the  infinity  of 
space,  there  would  still  result  this  ineffable  blaze  of 
light,  surpassing  the  light  of  day  as  greatly  as  the  vault 
of  heaven  surpasses  the  disk  of  the  sun.  And  this 
again  would  be  true,  though  this  system  of  systems 
were  limited  in  extent,  but  surrounded  by  similar  sys- 
tems of  systems  in  the  infinity  of  space.  And  so  on, 
let  the  order  of  systems  which  finally  becomes  infinite 
in  number  be  what  it  may.  There  is  only  one  way  to 
escape  from  this  limitless  series  of  system-orders — that 
is,  by  accepting  as  true  the  hypothesis  that  light  suffers 
extinction  as  it  voyages  through  space.  But  it  is  worth 
noticing,  when  we  are  actually  dealing  with  the  infini- 
ty of  space,  and  when,  therefore,  limitless  conceptions 
are  not  paradoxical,  but  in  reality  as  available  for  our 
purposes  as  finite  conceptions  would  be,  that  if  we  do 
adopt  the  belief  in  an  infinite  succession  of  orders  of 
systems,  that  is,  first  satellite-systems,  then  planetary 
systems,  then  star-systems,  then  systems  of  star-sys- 
tems, then  systems  of  systems  of  star-systems,  and  so 

star's  disk — k  being  inconceivably  large,  the  amount  received  from  the 
other  is  also  ^th  of  this  amount,  and  the  total  from  all  the  shells  must, 

therefore,  be  £  +  £  +  £  +  £ to  innnity- 

Now,  by  taking  k  terms  of  this  series  (or  k  shells  out  of  our  infinite 
series  of  shells),  we  should  get  unity,  that  is,  the  whole  heavens  lighted 
up  with  starlight  or  sunlight.  There  would  be  a  proportion  of  stars  in 
the  same  visual  line  and  so  hiding  each  other ;  but,  since  we  can  take 
2  &,  3  A:,  or  infinity  times  k  if  need  be,  there  can  be  no  doubt  the  whole 
heavens  woTild  be  lighted  up  with  solar  brightness. 


THE  NEBULAE.  2&5 

on  to  infinity,  and  if  we  accept  as  true  of  this  infinite 
series  what  we  know  to  be  true  of  the  part  within  our 
ken,  viz.,  that  the  distance  between  the  components 
forming  any  system  is  indefinitely  great  compared  with 
the  dimensions  of  those  components,  we  no  longer  have 
as  a  conclusion  that  the  whole  heavens  should  be 
lighted  up  with  stellar  (that  is  with  solar)  splendor ; 
even  though,  in  this  view  of  the  subject,  there  are  in 
reality  an  infinite  number  of  stars,  just  as  in  the  view 
according  to  which  the  sidereal  system  extends  with- 
out interruption  to  infinity.* 

But  whether  we  adopt  this  or  any  other  view  of 
the  way  in  which  external  systems  are  arranged,  this 
at  any  rate  is  certain,  that  if  the  stars  at  the  outer 

*  It  is  clear  that  we  no  longer  get,  as  in  the  previous  note,  a  series 
of  equal  small  terms.     If  we  take  our  infinite  series  of  shells  as  before, 

we  get  for  the  sidereal  system  n  tunes  -  where  n  is  finite  and  therefore 
?  finite.  We  must  indeed  assume  -  to  be  small,  and  so  of  other  similar 

ratios  presently  to  be  dealt  with.  With  respect  to  the  system  of  systems 
we  have  these  considerations  to  guide  us, — any  of  the  spherical  shells 
within  this  system  must  supply  to  our  skies  an  amount  of  light  indefi- 
nitely less  than  one  of  the  shells  within  the  sidereal  system  itself,  say 

_  th  part  only,  k'  indefinitely  large ;  but  the  number  of  shells  falling 

within  that  system  is  very  much  greater,  say  n'  times  as  great  where  n' 
is  finite.  Therefore  we  get  for  the  total  amount  of  light  coming  from 

the  system  of  systems  a  quantity  proportional  to  — ,  and  so  for  the 
system  of  system  of  systems  we  get  a  quantity  proportional  to  . 

where  k"  is  indefinitely  large,  n"  very  large.  And  for  each  successive 
order  we  get  a  multiplier  of  the  form  -,  where  K  is  indefinitely  large 

and  N  very  large  indeed.     Suppose  -  to  be  the  largest  of  all  these  multi- 


286  OTHER    WORLDS  THAN  OURS. 

parts  of  our  own  sidereal  system  be  beyond  the  ken  of 
our  most  powerful  instruments — and  I  have  shown 

pliers,  then  the  total  amount  of  light  received  from  the  infinite  system 
of  systems  is  proportional  to  less  than 

-+-^+  ,  ....  to  infinity  J} 

(in  which  v  is  supposed  to  be  less  than  K),  i.  e.,  to  less  than  -  (    *..  V  a 

k\K-v) 

finite  quantity,  which  will  even  be  minute  if  k  and  K  are  severally  much 
greater  than  n  and  v. 

This  particular  mode  of  escaping  from  the  difficulty  suggested  by 
the  illumination  of  the  heavens,  without  adopting  the  theory  that  light 
suffers  extinction  in  its  passage  through  space,  occurred  to  me  while  I  was 
preparing  a  series  of  papers  entitled  "A  New  Theory  of  the  Universe," 
which  appeared  in  The  Student  in  the  spring  of  1869,  and  I  there 
exhibit  the  considerations  just  dealt  with.  I  was  much  pleased  to  find, 
from  a  letter  of  Sir  John  Herschel's,  that  the  same  idea  had  suggested 
itself  to  him ;  as  I  was  thus  encouraged  to  believe  that  I  had  not  gone 
very  far  astray  in  the  whole  series  of  papers,  whereof  the  matter  in  ques- 
tion had  seemed  to  me  the  most  speculative  portion.  The  following  are 
the  words  in  which  Sir  John  Herschel,  writing  in  ignorance  of  my  having 
adopted  the  same  view,  expresses  the  ideas  above  dealt  with  :  "  One  of 
the  arguments  advanced  in  favor  of  the  spatial  extinction  of  light  was 
that,  if  there  is  not  such  extinction,  the  whole  heavens  ought  to-be  one 
blaze  of  solar  light — admitting  the  universe  to  be  infinite,  because  it  was 
contended  that  there  could  then  be  no  direction  hi  space  in  which  the 
visual  ray  would  not  encounter  a  star  (i.  e.,  a  sun).  This  argument  is 
fallacious,  for  it  is  easy  to  imagine  a  constitution  of  a  universe  literally 
infinite  which  would  allow  of  any  amount  of  such  directions  of  penetra- 
tion as  not  to  encounter  a  star.  Granting  that  it  consists  of  systems 
subdivided  according  to  the  law  thai  every  higher  order  of  bodies  in  it 
should  be  immensely  more  distant  from  the  centre  than  those  of  the  next 
inferior  order — this  would  happen.  Thus,  in  our  own,  the  moon  is  very 
near  the  earth,  the  satellites  to  their  primaries.  These  primaries  are 
immensely  more  distant  from  the  sun,  their  centre;  the  fixed  stars 
again  still  more  immensely  more  remote  from  the  sun.  Suppose  our 
system  to  terminate  with  the  visible  fixed  stars  ;  then  imagine  a  system 
of  such  systems  as  remote  from  each  other,  in  comparison  with  their  owt, 
dimensions,  as  the  distance  of  the  fixed  stars  in  comparison  with  the 
planetary  system ;  such  systems  seen  from  each  other  would  subtend 
no  greater  angle  than  a  star  seen  from  the  sun — and  so  on." 


THE  NEBULAE.  2g7 

tliat  there  are  strong  reasons  for  this  conclusion — then 
the  component  suns  of  external  galaxies  cannot  by  any 
possibility  be  visible.  So  that,  according  to  this  view, 
all  resolvable  nebulae,  at  least,  must  be  dismissed  from 
the  category  of  external  galaxies.  Nor  will  it  be 
thought  probable  that  irresolvable  nebulae  are  external 
galaxies,  if  once  that  view  of  the  extent  of  the  sidereal 
system  is  adopted. 

But  there  are  independent  considerations,  on  which 
I  prefer  now  to  dwell,  for  believing  that  all  the  nebulas 
belong  to  the  sidereal  system. 

It  will  hardly  be  necessary,  let  me  remark  in  pass- 
ing, for  me  to  point  out  how  this  matter  is  associated 
with  the  subject  of  other  worlds.  It  is  true  that,  when 
once  it  is  admitted  that  there  are  external  galaxies,  it 
may  be  looked  on  as  a  matter  of  small  importance  (so 
far  as  the  subject  of  this  treatise  is  concerned)  whether 
we  can  actually  see  those  galaxies  or  not.  I  am  not, 
for  instance,  in  the  same  position  as  Dr.  Whewell, 
who  assigned  to  the  nebulae  what  I  take  to  be  their 
true  place  in  the  universe,  with  the  express  object  of 
overthrowing  the  belief  that  there  exist  other  galaxies 
as  vast  as  the  sidereal  or  vaster,  thronged  with  suns 
which  are  severally  the  centres  of  planetary  systems, 
within  which  again  are  worlds  as  well  suited  to  be  the 
abode  of  life  as  this  earth  on  which  we  dwell.  But. 
though  my  purpose  is  different  from  his,  it  is  equally 
necessary  that  I  should  insist  on  the  true  position  of 
the  nebulas.  Because,  if  these  objects  form  indeed  part 
of  the  sidereal  system,  the  relations  they  present  are 
of  extreme  importance.  They  exhibit  to  us  within  the 


288  OTHER    WORLDS  THAN  OURS. 

bounds  of  our  galaxy  systems  altogether  different  from 
the  solar  system,  and  thus  suggest  ideas  of  other 
classes  of  worlds  peopled  with  their  own  peculiar  forms 
of  life,  as  distinct,  perchance,  even  in  their  general  char- 
acteristics, from  any  found  amid  the  systems  circling 
round  stars,  as  the  forms  of  life  in  Yenus  or  in  Mars 
must  be  in  their  special  characteristics  from  those  ex- 
isting on  our  own  earth. 

Freed  from  those  analogies  which  led  the  elder 
Herschel  to  regard  the  stellar  nebulae — resolvable  and 
irresolvable  * — as  external  star-systems,  let  us  consider 
the  relations  presented  by  these  and  other  nebulae, 
without  reference  to  preconceived  opinions. 

We  must  first  pay  attention  to  one  of  the  most 
striking  of  the  discoveries  which  the  spectroscope  has 
yet  enabled  man  to  make — the  discovery  that  certain 
nebulas  are  gaseous.  It  is  necessary  to  consider  this 
significant  discovery,  rather  than  those  which  were  the 
first  to  exhibit  the  real  place  of  the  nebulae  in  our 
scheme,  because  we  shall  thus  be  able  to  divide  the 
nebulae  at  once  into  two  great  classes,  instead  of  being 
led  to  this  arrangement  by  following'  out  the  history 
of  those  long  processes  of  research  by  which  the  two 
great  orders  of  nebulae  were  long  since  separated  from 
each  other  under  the  piercing  scrutiny  of  Sir  "William 
Herschel. 

The  reader  will  see  how  the  spectroscope  could  at 

*  By  irresolvable  stellar  nebulae,  I  mean  those  nebulae  which,  though 
not  resolvable  into  stars,  yet  present  the  characteristic  features  which 
lead  astronomers  to  believe  that  only  increase  of  telescopic  power  is 
needed  in  order  to  effect  resolution. 


THE  NEBULAE. 


289 


ance  resolve  a  question  which  ordinary  observations 
would  be  all  but  powerless  to  deal  with.  The  nebulae 
being  self-luminous,  the  nature  of  the  matter  which  is 
the  source  of  their  light  would  be  shown  by  the  char- 
acter of  the  spectrum,  as  distinctly  as  though  that 
matter  were  actually  present  in  the  laboratory  of  the 
spectroscopist. 

Mr.  Huggins  thus  describes  the  observation  which 
first  revealed  the  true  nature  of  certain  orders  of  the 
nebulae.  The  object  under  examination  was  a  nebula 
in  Draco,  belonging  to  the  class  of  planetary  nebulae : 
"  On  August  19,  1864:,  I  directed  the  telescope,  armed 
with  the  spectrum  apparatus,  to  this  nebula.  At  first 
I  suspected  some  derangement  of  the  instrument  had 
taken  place,  for  no  spectrum  was  seen,  but  only  a 
short  line  of  light  perpendicular  to  the  direction  of 
dispersion  (that  is,  to  what  would  in  the  case  of  solar 
light  be  the  length  of  the  spectrum).  I  then  found 
that  the  light  of  this  nebula,  unlike  any  other  ex-ter- 
restrial light  which  had  yet  been  subjected  by  me  to 
prismatic  analysis,  was  not  composed  of  light  of  differ- 
ent refrangibilities,  and  therefore  could  not  form  a 
spectrum.  A  great  part  of  the  light  from  this  nebula 
is  monochromatic,  and  after  passing  through  the 
prisms  remains  concentrated  in  a  bright  line,  occupy- 
ing the  position  of  that  part  of  the  spectrum  to  which 
its  light  corresponds  in  refrangibility.  A  more  care- 
ful examination,  however,  showed  that — a  little  more 
refrangible  than  the  bright  line,  and  separated  from  it 
by  a  dai-k  interval — a  narrower  and  much  fainter  line 
occurs.  Beyond  this  again,  at  about  three  times  the 
13 


290  OTHER   WORLDS  THAN  OURS. 

distance  of  the  second  line,  a  third  exceedingly  faint 
line  was  seen.  The  positions  of  these  lines  in  the 
spectrum  were  determined  by  a  simultaneous  com- 
parison of  them  in  the  instrument,  with  the  spectrum 
of  the  induction-spark  taken  between  electrodes  of 
magnesium.  The  strongest  line  coincides  in  position 
with  the  brightest  of  the  air-lines.  This  line  is  due  to 
nitrogen.  .  .  .  The  faintest  of  the  lines  of  the  nebu- 
la agrees  in  position  with  a  line  of  hydrogen.  The 
other  bright  line  was  not  found  to  correspond  with  a 
known  line  of  any  terrestrial  element.  Besides  the 
bright  lines,  an  exceedingly  faint  spectrum  was  just 
perceived  for  a  short  distance  on  both  sides  of  the 
group  of  bright  lines.  Mr.  Huggins  suspected  that 
this  was  not  uniform,  but  crossed  with  dark  spaces. 
Subsequent  observations  on  other  nebulae*  induced 
him  "  to  regard  this  faint  spectrum  as  due  to  the  solid 
or  liquid  matter  of  the  nucleus,  and  as  quite  distinct 
from  the  bright  lines  into  which  nearly  the  whole  of 
the  light  from  the  nebula  is  concentrated." 

*  One  of  the  most  interesting  of  Mr.  Huggins's  researches  into  the 
subject  of  the  light  of  nebulae  is  his  attempt  to  determine  its  intrinsic 
brilliancy.  By  comparing  the  light  of  certain  gaseous  nebulae  with  that 
of  a  sperm-candle  (of  the  size  called  six  to  the  pound),  he  found  that 
these  objects,  assumed  to  be  continuous,  shine  with  a  light  varying  in 
intrinsic  brilliancy  from  the  1,500th  to  the  20,000th  of  that  of  such  a 
candle.  By  a  strange  misconception,  Mr.  Lockyer,  in  discussing  Mr. 
Huggins's  result,  speaks  of  the  comparison  as  though  it  related  to  the 
absolute  brightness  of  the  nebulae,  saying  that  "  such  a  candle  a  quarter 
of  a  mile  off  is  20,000  times  more  brilliant  than  the  nebula."  Mr.  Hug. 
gins's  result  is  wholly  distinct  from  this,  and  much  more  important. 
His  comparison  relates  to  the  intrinsic  luminosity  of  the  nebular  sub- 
stance,  not  to  the  quantity  of  light  received  from  the  nebulas.  (The  dis- 
tance of  the  candle  in  Mr.  Huggins's  observations  is  not  considered  in 
the  result ;  it  was  a  mere  matter  of  convenience.) 


THE  NEBULA.  2gl 

Thus  was  solved  a  problem  which  had,  for  the  best 
part  of  a  century,  perplexed  astronomers.  There  was 
not,  indeed,  a  full  answer  to  all  the  questions  of  in- 
terest associated  with  the  problem.  But  it  had  been 
laid  down  by  Sir  William  Herschel,  as  a  legitimate 
conclusion  from  observation,  that  certain  orders  of  the 
nebulae  are  gaseous,  and  astronomers  had  ranged 
themselves  for  and  against  this  proposition.  Telesco- 
pic improvements  had  seemed  at  length  to  turn  the 
scale  in  favor  of  those  who  held  Sir  "William  Herschel 
to  have  been  mistaken.  Already  the  problem  had 
seemed  all  but  definitively  settled.  And  then  in  a  mo- 
ment this  observation  by  Mr.  Huggins  had  reversed 
the  whole  matter.  It  was  now  established,  beyond  all 
possibility  of  future  question,  that,  on  the  main  point, 
the  greatest  of  modern  astronomers  had  been  alto- 
gether in  the  right. 

The  orders  of  nebulae  which  give  a  spectrum  of 
bright  lines,  would  seem  from  Mr.  Huggins's  observa- 
tions to  be  (i.)  the  planetary  nebulas,  (ii.)  the  ring 
nebulae,  (iii.)  the  irregular  nebulae.  The  spiral  nebulae 
seem,  for  the  most  part,  to  give  a  continuous  spec- 
trum, but  some  of  these  objects  give  the  bright-line 
spectrum  indicative  of  gaseity.  The  orders  of  nebulae 
which  give  a  continuous  spectrum  appear  to  be  the 
following :  (i.)  star  groups,  (ii.)  clusters,  regular  and 
irregular,  and  (iii.)  easily  resolvable  nebulae.  Of  the 
irresolvable  nebulas  a  large  proportion  seem  to  be  gas- 
eous.* 

*  The  following  classification  of  nebulae  in  this  respect,  by  Lord  Ox- 
mantown,  is  interesting  as  indicating  the  results  of  observations  made 


19Z 


OTHER    WORLDS  THAN  OURS. 


Here,  then,  we  find  the  nebulae  ranged  into  two 
important  divisions,  apparently  separated  by  a  dis- 
tinct line  of  demarcation.  Yet  one  is  tempted  to  in- 
quire whether  these  divisions  may  not  in  reality  run 
into  each  other,  by  the  fact  that  among  nebulae  of  cer- 
tain orders  are  objects  belonging  to  both  divisions. 
And  the  fact  that,  beneath  the  bright-line  spectrum 
of  the  gaseous  nebulae,  a  faint  continuous  spectrum 
may  be  seen,  seems  also  to  point  in  the  same  direc- 
tion. We  know  that,  so  far  as  the  telescopic  appear- 
ance of  the  nebulae  is  concerned,  there  is  very  striking 
evidence  of  a  gradual  progression  from  clusters  to  irre- 
solvable nebulae,  and,  therefore,  we  are  led  to  inquire, 
whether  the  spectroscope  conveys  a  similar  lesson. 

Now,  this  question  could  only  be  answered  satisfac- 
torily by  the  observation  of  a  series  of  nebulae  having 
spectra  progressively  varying,  from  bright  lines  on  an 
almost  invisible  continuous  spectrum  to  a  continuous 
spectrum  with  the  same  bright  lines  superposed  on  it, 
but  almost  imperceptible,  because  their  brightness  so 
little  exceeded  that  of  the  continuous  spectrum.  "We 

with  so  powerful  an  instrument  as  the  great  Parsonstown  telescope  (the 
nix-feet  reflector) : 

Continuous     Gaseous 
Spectrum.      Spectrum, 
Clusters    .  10  0 


Certainly  or  probably  resolved  ?  . 
Certainly  or  probably  resolvable  ? 
Blue,  or  green,  no  resolvability  . 
No  resolvability  detected  . 


5  0 
10  6 

0  4 

6  5 


Total  observed        .        .        .         .31  15 

Adding  nebulae  not  observed  at  Parsonstown,  there  are  in  all  41  which 
exhibited  a  continuous  spectrum,  and  19  which  gave  a  spectrum  indica- 
tive of  gaseity. 


THE  NEBULAS.  293 

have  not  evidence  of  such  completeness.  But  Lieu- 
tenant Herschel  has  observed  in  the  southern  heavens 
a  clustering  nebula  with  a  continuous  spectrum,  on 
which  he  could  just  detect  the  three  bright  lines  seen 
in  the  spectra  of  the  gaseous  nebulas.  And,  so  far  as 
this  evidence  extends,  the  conclusion  is  obvious,  that 
the  various  orders  of  nebulas  are  orders  of  but  a  single 
famil y.  It  will  be  seen  presently  that  this  conclusion, 
which  is  strikingly  corroborated  by  other  evidence, 
has  a  very  important  bearing  on  the  views  we  are  to 
form  respecting  the  relations  between  the  nebulae  and 
the  sidereal  system. 

The  first  process  by  which  we  must  attempt  to 
form  a  correct  estimate  of  the  nebular  system  corre- 
sponds to  Sir  William  Herschel's  process  of  star-gaug- 
ing. We  must  inquire  according  to  what  general 
laws  the  nebulae  are  spread  over  the  vault  of  heaven. 

Kow,  when  this  is  done,  it  appears  that  there  is  a 
well-marked  peculiarity  in  the  arrangement  of  the 
nebulae,  a  peculiarity  as  striking  as  the  existence  of 
the  galactic  circle  itself.  The  nebulcB  seem  to  withdraw 
themselves  from  the  neighborhood  of  the  galaxy.  In 
the  northern  heavens  they  cluster  very  definitely 
toward  the  pole  of  the  galaxy ;  in  the  southern  they 
are  arranged  in  streams  and  clustering  aggregations, 
but  the  galaxy  itself  is,  in  either  case,  left  almost  clear 
of  nebulae. 

If  this  peculiarity  is  accidental,  the  coincidence 
involved  is  most  remarkable.  Had  there  been  a  zone 
of  nebulae,  and  that  zone  had  shown  a  tendency  to 
coincidence  with  the  Milky  Way,  the  relation  would 


294 


OTHER   WORLDS  THAN  OURS. 


have  been  held  strikingly  indicative  of  a  real  associa- 
tion between  the  nebular  and  the  sidereal  systems. 
But  is  the  direct  converse  of  this  relation  more  likely 
to  be  the  effect  of  chance  ?  Have  not  observers  and 
experimenters  concluded  (in  every  other  similar  in- 
stance) that  a  law  of  contrast  is  as  indicative  of  a  real 
connection  as  a  law  of  association  ?  It  is  surprising, 
therefore,  that  nearly  all  astronomers,  who  have  con- 
sidered the  relation  in  question,  have  regarded  it  as 
affording  strong  evidence  that  the  nebular  system  is 
wholly  dissociated  from  the  sidereal. 

Next  let  us  turn  to  special  features.  In  the  first 
place,  let  us  inquire  whether  the  different  orders  of 
nebulae  exhibit  any  peculiarities  of  arrangement. 

We  find  that  clusters  exhibit  a  very  marked  pref- 
erence for  the  neighborhood  of  the  Milky  Way ;  re- 
solvable nebulae  seem  to  prefer  the  galactic  zone,  but 
not  in  so  decided  a  manner  ;  and  it  is  only  among  the 
irresolvable  nebulae  that  we  recognize  that  withdrawal 
from  the  Milky  Way  which  had  seemed  character- 
istic of  the  whole  nebular  system,  before  we  consid- 
ered its  several  orders.  The  fact  that  the  irresolvable 
nebulas  form  about  four-fifths  of  the  total  number  will 
account  for  the  circumstance  that  a  peculiarity  really 
appertaining  to  that  order  alone  should  appear  to  be- 
long to  the  whole  system  of  nebulae. 

Again,  the  planetary  and  irregular  nebulae  are 
found  to  affect  the  neighborhood  of  the  Milky  Way.  I 
have  already  mentioned  that  these  objects  are  gaseous. 

It  is  easy  to  see  what  general  conclusions  may  be 
deduced  from  the  peculiarities  here  touched  upon. 


THE  NEBULAE.  2g^ 

Obviously  the  first  shows  us  most  distinctly  that  there 
is  a  relation  between  propinquity  to  the  Milky  Way 
and  the  character  of  nebulae  as  respects  resolvability— 
a  relation  which  points  in  the  most  decisive  manner 
to  the  existence  of  a  close  association  between  the  side- 
real system,  of  which  the  Milky  Way  certainly  forms 
part,  and  the  nebular  system,  from  which  clusters  and 
resolvable  nebulas  cannot  reasonably  be  separated.  It 
is  equally  obvious  that  the  second  peculiarity  indicates 
the  existence  of  a  close  association  between  the  Milky 
"Way  and  the  character  of  the  nebulas  as  respects  ga- 
seity ;  a  relation  which  brings  all  the  gaseous  nebulas 
into  close  association  with  the  sidereal  system,  since 
we  know  that  among  the  extra-galactic  nebulas  there 
are  many  which  are  principally  formed  of  the  very 
same  gases  which  appear  in  the  irregular  and  planet- 
ary nebulas.  When  we  consider  that  those  peculiar- 
ities of  configuration  and  of  constitution  which  have 
alike  seemed  to  indicate  that  the  various  orders  of 
nebulas  merge  into  each  other  by  indefinable  grada- 
tions are  both  associated,  in  a  very  distinct  manner, 
with  the  most  marked  peculiarity  of  the  sidereal  sys- 
tem, and  when  to  this  we  add  what  has  been  already 
suggested  by  the  relation  of  contrast  between  the  ir- 
resolvable nebulas  and  the  Milky  Way,  the  conclusion 
seems  forcibly  impressed  upon  us  that  the  nebular  and 
the  sidereal  systems  are  but  different  parts  of  one  sin- 
gle scheme. 

But  I  pass  on  to  other  evidence,  independent  of 
what  has  hitherto  been  adduced,  and  pointing  with 
equal  force  to  the  same  conclusion. 


296  OTHER   WORLDS  THAN  OURS. 

In  the  northern  heavens  it  is  not  very  easy  to  ex- 
hibit any  general  law  of  arrangement  associating  the 
nebulae  and  the  fixed  stars.  For  reasons  which  yet 
remain  to  be  detected,  there  are  in  fact  many  marked 
points  of  difference  between  the  whole  character  of  the 
heavens  on  the  northern  and  on  the  southern  side  of 
the  galactic  zone.  But  even  in  the  northern  heavens 
one  peculiarity  has  been  remarked,  which  is  well 
worthy  of  careful  consideration.  Sir  "William  Her- 
schel,  while  prosecuting  his  series  of  researches  among 
stars  and  nebulae,  was  struck  by  the  circumstance 
that,  after  sweeping  over  a  part  of  the  heavens  which 
was  unusually  barren,  he  commonly  met  with  nebulae  ; 
insomuch  that  it  was  his  practice  at  such  times  to 
call  to  his  assistant  (his  sister,  Miss  Caroline  Herschel) 
to  "  prepare  for  nebulae."  This  peculiarity  was  noticed 
also  by  Sir  John  Herschel. 

Now,  what  are  we  to  understand  by  such  a  relation 
as  this  ?  Can  we  suppose  that,  owing  to  some  strange 
accident,  external  galaxies  have  been  placed  always 
opposite  the  barest  regions  of  the  sidereal  system  ?  Or, 
setting  aside  such  a  notion  as  obviously  incredible,  are 
we  to  imagine  that,  when  searching  over  those  barren 
regions,  the  astronomer  has  a  better  chance  of  detecting 
nebulae  than  where  stars  are  more  richly  strewn,  be- 
cause the  sky  is  less  filled  with  glare  ?  We  are  forced 
to  dismiss  this  notion,  that  the  barren  regions  of  the 
heavens  are  thus  in  a  manner  the  spy -holes  of  the 
sidereal  system,  by  the  fact  (presently,  and  for  another 
purpose,  to  be  dwelt  on  more  at  length)  that  in  the 
Magellanic  Clouds,  where  stars  of  all  magnitudes  are 


THE  NEBULAE.  2g7 

richly  strewn,  nebulae,  even  down  to  the  very  faintest 
orders,  are  more  abundant  than  in  any  other  region  of 
the  heavens.  "We  have,  then,  no  other  conclusion  to 
form,  but  that  the  association  thus  observed  between 
starless  regions  and  richness  of  nebular  distribution 
indicates  a  very  close  relation  indeed  between  stars  and 
nebulae ;  that,  in  fact,  the  nebulae  in  a  sense  represent 
the  missing  stars  /  that  the  region  where  those  nebulcs 
appear  has  been  drained  of  star-material,  so  to  speak, 
in  order  to  form  them. 

In  the  southern  heavens  yet  clearer  proof  exists 
of  an  association  between  the  stellar  and  nebular  sys- 
tems. We  do  not  recognize  in  the  northern  skies  any 
well-marked  star-streams.  In  the  southern  skies,  how- 
ever, such  streams  have  been  recognized  from  the 
earliest  ages.  The  constellations  Hydra  and  Eridanus, 
the  two  streams  from  the  Water-can  of  Aquarius,  and 
the  band  between  the  two  fishes,*  indicate  how  clearly 
the  ancients  traced  certain  well-marked  star-streams. 
The  moderns  have  traced  the  extension  of  some  of 
these  streams  in  the  constellations  Grus,  Hydra,  Re- 
ticulum,  etc.,  into  the  near  neighborhood  of  the  south- 
ern pole.  Now,  the  nebulae  in  the  southern  heavens 
exhibit  a  well-marked  tendency  to  aggregate  into 
streams.  So  that,  in  this  mere  resemblance  between 
the  general  characteristics  of  the  stellar  and  nebular 
systems  in  the  southern  heavens,  we  have  a  somewhat 
remarkable  evidence  of  association.  But  when  we 

*  Though  Pisces  is  not  a  southern  constellation,  yet  it  is  south  of 
the  galactic  circle,  to  which  I  am  for  the  moment  referring  the  con- 
stellations. 


298  OTHER   WORLDS  THAN  OUR8. 

consider  the  disposition  of  the  two  sets  of  streams — 
the  stellar  and  the  nebular — this  evidence  is  very 
much  strengthened.  There  is  found  to  be  a  well- 
marked  correspondence  between  the  nebular  and  stel- 
lar streams,  not  merely  as  respects  general  position, 
but  even  in  minute  details — the  nebular  streams  fol- 
lowing the  windings  of  the  stellar  ones.  Such  a  rela- 
tion would  be  very  remarkable,  even  were  it  observed 
but  in  a  single  instance.  Since,  however,  all  the  well- 
marked  star-streams  in  the  southern  heavens  are  asso- 
ciated with  well-marked  nebular  streams,  no  doubt 
can  remain  that  the  relation  is  not  a  mere  coincidence, 
but  indicates  a  real  association  between  the  nebular 
and  stellar  systems. 

But  yet  more  striking  evidence  remains  to  be  con- 
sidered. 

In  the  southern  heavens  there  are  two  strange 
clouds  of  milky  light,  which  have  long  been  known 
by  sailors  as  the  Magellanic  Clouds,  but  are  commonly 
called  by  astronomers  the  Nubeculas.  Each  of  these 
objects,  when  examined  with  the  telescope,  is  found 
to  be  constituted,  like  the  Milky  Way,  of  multitudes 
of  small  stars.  But,  unlike  the  Milky  Way,  the 
Nubeculae  contain  within  their  bounds  many  nebulae 
of  all  orders.  In  fact,  each  of  the  Nubeculae  is  at 
once  a  star-cluster  and  a  cluster  of  nebulae. 

Now,  there  can  be  no  doubt  whatever  that  the  as- 
sociation here  is  not  accidental,  that  we  do  not  by 
some  strange  chance  see  a  great  star-cluster  in  the 
same  direction  as  a  much  more  distant  and  much 
vaster  cluster  of  external  galaxies.  Nor,  again,  can 


THE  NEBULAE.  2g9 

there  be  any  doubt  that  the  generally  circular  figure 
of  each  Nubecula  indicates  a  general  approach  to  the 
spherical  form  in  the  case  of  each  cluster.  The  prob- 
ability that  by  some  strange  accident  a  cluster  of 
cylindrical  shape  *  might  be  so  placed  as  to  exhibit  to 
us  a  circular  figure  is  exceedingly  small;  but  the 
chance  that  two  such  clusters  should  be  presented  in 
so  exceptional  a  manner  may  be  regarded  as  evanes- 
cent. We  are  compelled,  then,  to  believe  that,  within 
the  limits  of  spheres  so  placed  as  to  subtend  a  small 
angle  to  the  eye,  stars  of  all  magnitudes  between  the 
seventh  and  the  twelfth  inclusive  are  mixed  up  with 
nebulae  of  all  degrees  of  resolvability.  "  Taking  the 
apparent  semi-diameter  of  the  Nubecula  Major  at  three 
degrees,"  says  Sir  John  Herschel,  "  and  regarding  its 
solid  form  as,  roughly  speaking,  spherical,  its  nearest 
and  most  remote  parts  differ  in  their  distance  from  us 
by  a  little  more  than  a  tenth  part  of  our  distance  from 
its  centre."  "  It  must  therefore  be  taken  as  a  demon- 
strated fact,"  he  adds  presently,  "  that  stars  of  the 
seventh  and  eighth  magnitude  and  irresolvable  nebulae 
may  coexist  within  limits  of  distance  not  differing  in 
proportion  more  than  as  nine  to  ten."  This  demon- 
strated fact  of  Sir  John  Herschel's  is  the  very  fact  to 
which  I  had  been  led  by  other  considerations,  the  fact, 
namely,  that  the  nebulas  are  not  external  galaxies,  but 
intimately  associated  with  the  sidereal  system  of 
which  in  fact  they  form  part  and  parcel.  Dr.  Whe- 
well,  accepting  Sir  John  Herschel's  reasoning  as  con- 

*  Or,  more  correctly,  a  cluster  shaped  like  a  long  frustum  of  a  gigan- 
tic cone. 


JOO 


OTHER   WORLDS  THAN  OURS, 


elusive  on  the  point,  adopted  the  same  view.  Tet  Sir 
John  Herschel  himself  seems,  immediately  after  estab- 
lishing this  noteworthy  conclusion,  to  have  been  pre- 
pared to  abandon  it,  at  least  as  a  demonstrated  fact, 
since  he  says  of  it  only  that  "  it  must  inspire  some  de- 
gree of  caution  in  admitting  as  certain  "  facts  directly 
opposed  to  it.  It  must  not  be  forgotten,  however, 
that  to  the  clear  vision  of  this  great  astronomer  the 
association  between  nebuloe  and  fixed  stars  had  pre- 
sented itself  as  a  demonstrated  fact ;  that  even  in  the 
latest  editions  of  his  noble  work  on  astronomy,  he  has 
not  altered  the  words  in  which  he  has  spoken  of  that 
association ;  and  that  so  able  a  reasoner  as  Dr.  Whe- 
well  has  chosen  rather  to  accept  what  Herschel  has 
spoken  of  as  a  demonstrated  fact,  than  to  adopt  that 
measure  of  caution  which  Herschel  subsequently  ad- 
vocated. 

Lastly,  and  perhaps  most  strikingly  of  all,  the  asso- 
ciation between  stars  and  nebulae  is  indicated  by  the 
obvious  connection  between  the  figure  of  the  irregular 
nebulas  and  the  arrangement  of  the  star-groups  seen 
in  the  same  field  of  view.  There  is  not  one  of  the 
irregular  nebulae  which  does  not  exhibit  this  pecu- 
liarity in  the  most  striking  manner.  This  may  be 
asserted  even  of  those  nebulae  with  respect  to  which 
Sir  John  Herschel  has  remarked  that  the  arrangement 
may  be,  and  probably  is,  purely  accidental.  His  own 
pictures  prove  in  the  most  convincing  manner  that  no 
such  explanation  can  be  accepted.  Were  the  peculi- 
arity confined  to  the  feature  Herschel  limits  his  atten- 
tion to,  one  might  adopt  his  explanation.  The  mere 


THE  NEBULA.  3O| 

aggregation  of  a  large  number  of  stars  on  the  very 
heart  of  a  nebula  might  be  an  accident.  The  fact, 
for  instance,  that  the  great  irregular  nebula  surround- 
ing the  star  Eta  Argus  agrees  exactly  in  position 
with  the  greatest  condensation  of  the  wonderfully  rich 
portion  of  the  Milky  "Way  on  which  that  surprising 
variable  lies,  might  be  a  mere  coincidence,  though  in 
any  case  it  would  be  a  strange  one.  But  when  one 
examines  the  structure  of  this  and  similar  nebulae,  and 
finds  that  the  stars  are  arranged  in  a  manner  most  ob- 
viously related  to  the  arrangement  of  the  nebular  con- 
densations (or  folds  as  one  may  almost  say),  one  can- 
not doubt  that  a  real  and  intimate  bond  of  association 
exists  between  the  stars  and  the  nebulous  masses 
around  them.  If  the  extension  of  the  milky  light  of 
the  great  Orion  nebula  to  the  star  in  the  sword,  which 
is  centrally  involved  in  strong  nebulosity,  to  e  in  the 
belt,  which  is  similarly  involved,  and  to  several  other 
stars  in  the  constellation  all  alike  in  being  regions 
of  increased  nebular  condensation,  be  a  mere  acci- 
dental coincidence,  then  the  laws  of  probability  had 
better  be  forgotten  as  soon  as  possible,  for,  as  at  pres- 
ent understood,  they  can  only  serve  to  lead  men 
astray. 

In  the  accompanying  plate  is  given  a  picture  of 
the  nebula,  Messier  17,  as  observed  with  Lassell's 
four-feet  reflector  at  Malta.  I  have  selected  it  as  af- 
fording a  very  striking  instance  of  the  particular  form 
of  association  I  have  just  been  dealing  with.  No  one 
can,  I  think,  refuse  to  recognize  the  fact  that  the  sys- 
tem of  stars  shown  in  this  drawing  is  not  accidentally 


302 


OTHER    WORLDS   THAN  OURS. 


seen  projected  on  a  distant  galaxy,  but  forms  part  and 
parcel  of  the  nebula  itself. 

It  will  be  noticed,  as  respects  the  two  proofs  on 
which  I  have  last  dwelt,  that  they  seem  directly  op- 
posed to  those  which  I  first  quoted.  One  cannot 
argue,  it  might  be  urged,  that  the  nebulae  are  asso- 
ciated with  the  sidereal  system  because  they  are  least 
numerous  where  there  are  most  stars,  and  vice  versa  ; 
while  at  the  same  time  one  draws  the  same  conclusion 
from  the  aggregation  of  the  nebulae  in  streams  or  clus- 
ters where  there  are  streams  and  clusters  of"  stars,  or 
from  the  fact  that  stars  are  seen  actually  mixed  up 
with  nebulous  matter.  At  first  sight  this  objection 
seems  just ;  but,  on  consideration,  it  will  be  found  that, 
in  reality,  the  two  seemingly  contrary  lines  of  argu- 
ment bear  in  the  same  direction.  "When  we  find  the 
nebulae  gathered  where  stars  are  wanting,  and  vice 
versa,  we  conclude  that  there  is  some  reason  for  this 
peculiarity,  and  that  that  reason  must  involve  some 
sort  of  association  between  the  nebulae  and  the  stars ; 
we  see,  further,  that  the  relation  is  accounted  for  if  we 
suppose  that,  in  these  cases,  either  the  formation  of 
nebulae  has  drained  a  region  of  material  from  which 
single  stars  would  otherwise  have  been  formed,  or  vice 
versa,  Why,  in  a  particular  region,  the  formation  of 
nebulas  should  be  encouraged,  while  the  formation  of 
stars  should  be  checked,  we  cannot  say;  nor  can  we 
account  for  the  contrary  peculiarity  in  another  region  ; 
but  we  feel  certain  that  some  cause  must  exist  for  both 
relations,  because  the  results  are  too  marked  to  be  the 
result  of  accident.  Now,  in  the  case  where  we  find 


THE  NEBULAE.  3O3 

botli  stars  and  nebulae  abundant  in  particular  parts  of 
the  heavens,  we  feel  equally  certain  that  the  result  is 
not  accidental.  Even  though  there  were  not  here,  as 
in  the  former  case,  the  evidence  of  a  clearing  of  star- 
material  from  certain  regions,  we  could  not  doubt  that 
the  association  of  stars  and  nebulae  was  real  and  not 
apparent.  But  in  reality  there  is  here,  precisely  as  in 
the  former  case,  a  gathering  together  of  stellar  matter 
into  certain  regions.  The  very  existence  of  such  a 
stream  as  Eridanus  or  Hydra,  and  of  such  a  cluster  as 
the  greater  or  lesser  Magellanic  Cloud,  implies  the  ac- 
tion of  such  a  process  of  segregation.  A  stream  would 
not  be  recognizable  if  it  were  not  bounded  by  relatively 
bare  regions.  Clusters  like  the  Nubeculse  might  be 
visible  even  on  a  rich  sky,  and  were  the  sidereal  heav- 
ens richly  strewed  with  stars  round  these  objects  I 
should  be  disposed  to  admit  that  there  was  a  difficulty 
in  my  theory.  But  what  is  the  fact?  Not  only  is 
each  of  the  ISTubeculae  placed  in  a  region  obviously 
bare  of  lucid  stars,  but  Sir  John  Herschel,  speaking  of 
the  telescopic  aspect  of  the  neighborhood  of  these  mys- 
terious clusters,  dwells  again  and  again  on  its  poverty. 
"  A  miserably  poor  and  barren  region,"  he  says  of  one 
field  near  the  Nubeculae.  "  The  access  to  the  Nubec- 
ulae,"  he  says  elsewhere,  "is  on  all  sides  through  a 
desert"  What  evidence  could  more  clearly  point  to 
the  fact  that  these  great  clusters  are  gathered  out 
from  a  vast  region  of  space  ?  Their  internal  structure 
teaches  us  how  such  a  process  of  segregation  leads  to 
the  birth  of  nebulas,  as  well  as  stars.  The  whole  his- 
tory of  the  sidereal  system  is  indeed  taught  us  in  the 


3°4 


OTHER   WORLDS  THAN  OURS. 


Magellanic  Clouds  and  the  great  streams  of  inter- 
mixed stars  and  nebulae  which  flow  toward  them  as 
rivers  toward  some  mighty  lake.  "We  see  the  wonder- 
working forces  of  gravitation  extending  their  influ- 
ences throughout  vast  regions  of  space,  gathering  in 
the  materials  spread  throughout  that  space,  here  form- 
ing stars,  there  nebulae,  changing  the  element  of  dis- 
tance into  various  forms  of  force — heat  and  light, 
electricity  and  magnetism — and  finally  (though  in 
what  special  way  we  are  as  yet  unable  to  perceive) 
making  the  orbs  which  it  has  formed  the  seats  of  life, 
or  subservient,  more  or  less  directly,  to  the  wants  of 
living  creatures. 


CHAPTER  XIII. 

SUPERVISION   AND   CONTROL. 

IT  has  been  customary,  in  treatises  on  the  plural- 
ity of  worlds,  to  discuss  the  religious  difficulties  which 
seem  to  suggest  themselves  when  man  regards  the  uni- 
verse around  him  as  thronged  with  worlds,  each  peo- 
pled with  millions  of  living  creatures,  and  many  per- 
chance the  abode  of  intelligent  and  therefore  respon- 
sible beings.  Accustomed  to  regard  himself  as  in  a 
special  manner  the  object  of  God's  care  and  solicitude, 
it  is  not  without  a  sense  of  pain  that  he  is  brought  to 
contemplate  the  possibility  that  other  creatures  may 
exist  in  uncounted  millions  whom  God  regards  with 
infinite  love  and  interest.  "  If  this  be  so,"  asks  "Whe- 
well,  "how  shall  the  earth  and  men,  its  inhabitants, 
annihilated  as  it  were  by  the  magnitude  of  the  known 
universe,  continue  to  be  any  thing  in  the  regard  of 
Him  who  embraces  all  ?  Least  of  all,  how  shall  men 
continue  to  receive  that  special,  preserving,  providen- 
tial, judicial,  personal  care,  which  religion  implies; 
and  without  the  belief  in  which,  any  man  who  lias  re- 
ligious thoughts  must  be  disturbed  and  unhappy,  deso- 
late and  forsaken  ?  " 


306 


OTHER   WORLDS  THAN  OURS. 


I  do  not,  however,  feel  by  any  means  invited  to 
consider  "  the  religious  difficulty  "  by  the  success  which 
has  attended  the  efforts  made  by  others  to  remove  it. 
I  find  that,  while,  on  the  one  hand,  the  thoughtful 
and  conscientious  men  who  have  in  a  special  manner 
considered  the  difficulty  have  been  (in  relation  at 
least  to  revealed  religion)  at  issue  among  each  other, 
their  views  have  not,  on  the  other  hand,  been  found 
acceptable  even  by  a  few  among  their  readers.  I 
doubt  almost,  when  I  judge  from  the  comments  which 
have  been  made  on  this  part  of  the  works  of  Chal- 
mers, Whewell,  Brewster,  and  others,  whether  a  sin- 
gle reader  of  those  works  has  found  the  religious 
views  of  any  one  of  their  authors  congenial  with  his 
own. 

It  is  specially  noteworthy  that  even  where,  as 
in  the  case  of  Brewster  and  Chalmers,  two  writers 
adopt  the  same  view  of  the  general  question  of  other 
worlds,  they  yet  hold  altogether  different  views  as  to 
the  bearing  of  that  question  upon  the  subject  of 
religion. 

It  is  very  doubtful,  therefore,  whether  it  is  a  wise 
thing,  whether  it  is  conducive  to  the  purpose  of  any 
one  thus  conscientiously  discussing  the  religious  aspect 
of  our  question,  to  present  his  own  personal  views 
on  the  subject  of  revealed  religion.  If  I  thought 
otherwise,  I  should  not  shrink  from  the  task  of  indi- 
cating the  sufficiently  definite  views  which  I  entertain 
myself  upon  this  subject.  But  I  apprehend  that,  apart 
from  the  consideration  that  the  reader  must  be  wholly 
indifferent  about  them,  my  indicating  them  would  have 


SUPERVISION  AND   CONTROL. 


307 


aii  effect  the  very  reverse  of  that  which  1  should 
desire.* 

Merely  remarking,  therefore,  that  in  considering 
the  infinity  of  God's  beneficence  we  must  remember 
this  quality  of  infinity,  that  it  comprises  many  infini 
ties,  I  pass  on  to  considerations  which  seem  to  fall 
more  naturally  within  the  province  of  the  student  of 
science. 

It  is  a  peculiarity  of  the  subject  of  other  worlds 
than  ours,  that  it  suggests,  more  strikingly  than  any 
other,  certain  difficulties  in  connection  with  the  con- 
ceptions we  are  to  form  as  to  the  supervision  and  con- 
trol exercised  by  the  Creator  over  His  works.  We 
feel  that  if  we  are  to  believe,  as  we  must  believe,  in 
an  infinitely  powerful  and  wise  God,  we  must  not 
merely  regard  all  the  worlds  which  people  space  as 
objects  of  His  regard,  but  every  event,  however  seem- 
ingly insignificant,  occurring  in  any,  even  the  least 
important  of  His  worlds,  as  an  essential  part  of  the 
plan  according  to  which  all  things  were  created  from 
the  beginning. 

*  Where  Bacon  has  selected  to  be  silent,  few  can  without  presump- 
tion venture  to  lay  down  their  opinions  as  of  weight  in  matters  con- 
nected with  revealed  religion.  The  argument  which  follows  may  not 
indeed  be  acceptable  to  many,  but  few  will  doubt  the  wisdom  of  the  con- 
clusion to  which  he  comes.  "  If  we  were  disposed,"  he  says,  "  to  sur- 
vey the  realm  of  sacred  or  inspired  theology,  we  must  quit  the  small 
vessel  of  human  reason,  and  put  ourselves  on  board  the  ship  of  the 
Church,  which  alone  possesses  the  Divine  needle  for  justly  shaping  the 
course.  Nor  will  the  stars  of  philosophy,  that  have  hitherto  principally 
lent  their  light,  be  of  further  service  to  us;  and  therefore  it  were 
not  improper  to  be  silent  upon  the  subject." — Advancement  of  Learning, 
Book  IX. 


3o8  OTHER  WORLDS  THAN  OURS. 

But  here  already — such  is  the  nature  of  the  subject 
I  am  to  deal  with — I  have  been  forced  to  use  terms 
which  have  really  no  proper  application  to  the  Al- 
mighty and  His  works.  I  have  spoken  of  the  creation 
of  all  things,  whereas,  in  the  sense  in  which  men  can 
alone  interpret  such  words,  we  cannot  reasonably  con- 
ceive that  there  ever  was  a  creation  ;  and  I  have 
spoken  of  the  beginning,  whereas  we  cannot  conceive 
that  there  ever  was  a  beginning  in  the  sense  implied.* 

Let  us  consider  definitely  (even  though  we  must  be 
unable  to  conceive  clearly  or  at  all)  the  infinities  we 
have  to  deal  with. 

We  know  that  space  must  be  infinite.  If  the  re- 
gion amid  which  stars  and  nebulae  are  scattered  with 
so  great  profusion  be  limited,  if  beyond  lies  on  all  sides 
a  vast  void,  or  if,  instead,  there  be  material  bounds 
enclosing  the  universe  of  worlds  on  every  hand,  yet 
where  are  the  limits  of  void  or  bound  ?  Infinity  of 
space,  occupied  or  unoccupied,  there  must  undoubted- 
ly be.  Of  this  infinity  it  has  been  finely  said,  that  its 
centre  is  everywhere,  its  boundary  nowhere.  Now, 
whether  within  this  infinity  of  space  there  be  an  infin- 
ity of  matter,  is  a  question  which  we  cannot  so  cer- 
tainly answer.  Only,  if  we  were  to  accept  this  as  cer- 
tain, that  the  proportion  which  unoccupied  bears  to 
occupied  space  cannot  be  infinitely  great — a  view 
which  at  least  seems  reasonable  and  probable — then  it 
would  follow  that  matter  as  well  as  space  must  be  in- 

*  To  prevent  any  possibility  of  my  meaning  being  misinterpreted 
here,  I  point  out  that  I  have  been  obliged  myself  to  use  the  terms  of 
which  I  speak  as  inexact. 


SUPERVISION  AND  CONTROL.  ^Og 

finite,  since  any  finite  proportion  of  infinity  must  it- 
self also  be  infinite.  So  that,  regarding  occupied  space 
as  the  realm  over  which  the  Almighty's  control  is  ex- 
ercised, and  -over  which  His  supervision  extends,  we 
find  just  reason  for  looking  upon  that  realm  as  no  less 
infinite  than  the  infinity  of  space  in  which  it  is  con- 
tained. 

Time  also  must  undoubtedly  be  infinite.  If  the 
portion  of  time  which  has  hitherto  been,  or  which  will 
hereafter  be,  occupied  with  the  occurrence  of  events 
(of  whatever  sort)  were  preceded  and  will  be  followed 
by  a  vast  void  interval,  yet  there  can  be  neither  be- 
ginning nor  end  to  either  of  those  bounding  voids. 
Infinity  of  time,  occupied  or  unoccupied,  there  must 
undoubtedly  be.  And,  though  it  is  not  possible  for  us 
to  know  certainly  that  there  has  been  no  beginning, 
or  that  there  will  be  no  end  to  that  portion  of  time 
which  is  occupied  with  the  occurrence  of  events  (of 
whatever  sort),  yet  it  appears  so  unreasonable  to  con- 
ceive that  unoccupied  time  bears  an  infinitely  great 
proportion  to  occupied  time,  that  we  seem  forced  to 
the  conclusion  that  occupied  time  is  infinite — or,  more 
definitely,  that  there  has  been  no  beginning  and  will 
be  no  end  to  the  sequence  of  events  throughout  the 
infinitely-extended  realm  of  the  Almighty. 

And  thus  we  are  forced  to  believe  in  the  infinite 
wisdom  and  the  infinite  power  of  God  ;  since  to  con 
ceive  of  limits  to  the  wisdom  and  power  of  Him  whose 
realm  is  infinite  in  extent  and  in  duration,  is  obviously 
to  conclude  that  the  Ruler  is  infinitely  incompetent  to 
rule  over  His  kingdom  ;  for  there  can  be  no  relation 


jio 


OTHER   WORLDS  THAN  OURS. 


between  the  finite  and  the  infinite  save  the  relation  of 
infinite  disproportion. 

Now,  although  the  conception  of  God  as  a  spirit — 
omnipresent,  eternal,  omnipotent,  and  omniscient — is 
altogether  beyond  the  powers  of  man's  imagination, 
yet  we  may  consider  certain  relations  between  the  way 
in  which  He  views  the  universe  and  the  modes  in  which 
we  men  consider  the  various  matters  falling  either  un- 
der our  supervision  and  partial  control,  or  of  which 
we  can  in  any  way  or  to  any  extent  become  cognizant. 

Senses  such  as  we  have  we  can  no  more  attribute 
to  God  than  we  can  assign  to  Him  hands  and  feet. 
Nor  can  we  conceive  in  what  way  a  spirit,  as  He  is,  ia 
cognizant  of  material  processes  which  we  only  recog- 
nize through  their  material  effects.  Yet,  as  we  do  not 
doubt  that  God  is  cognizant  of  the  actual  state  of  the 
universe  at  any  moment,  we  cannot  doubt  that  He  is 
cognizant  of  all  those  processes  by  which  our  senses 
can  be  affected.  And  clearly,  He  not  only  recognizes 
all  these  processes  in  such  sort  that  he  may  be  said  to 
see  what  we  see,  to  hear  what  we  hear,  and  so  on  ;  but 
effects  which,  though  related  to  vision,  hearing,  or  the 
like,  are  infinitely  too  minute  to  be  appreciated  by  our 
senses,  must  be  as  obvious  to  God  as  the  light  of  day 
or  the  roar  of  thunder  to  ourselves. 

But,  before  considering  the  nature  of  God's  super 
vision  of  His  universe,  we  may  proceed  a  step  farther. 
The  senses  we  possess  are  sufficient  to  indicate  to  us 
the  possible  existence  of  senses  not  merely  far  more 
acute,  but  of  a  wholly  different  kind.  By  the  sense 
of  touch,  for  instance,  we  can  indeed  recognize  the 


SUPERVISION  AND  CONTROL.  311 

feeling  of  heat ;  but  it  is  easy  to  conceive  of  a  sense 
(analogous  to  that  by  which  light  is  made  to  teach  us 
of  the  aspect  of  external  objects)  enabling  men  to  judge 
of  the  figure,  substance,  internal  structure,  and  other 
qualities  of  an  object,  by  the  action  of  the  heat-waves 
proceeding  from  it.  Or  again  electricity  might,  in- 
stead either  of  light  or  of  heat,  be  the  means  of  com- 
municating intelligence  as  to  the  qualities  of  objects. 
We  can  conceive  also  of  a  sense  bearing  the  same 
analogy  to  sight  that  the  spectroscope  bears  to  the 
telescope.  And  a  hundred  kinds  of  sense,  or  in  other 
words,  a  hundred  modes  of  receiving  intelligence  about 
what  exists  or  is  going  on  around  us,  might  be  readily 
conceived.  Now,  we  cannot  doubt  that  the  natural 
processes  involved  in  every  such  mode  of  conveying 
impressions  to  material  creatures  must  be  infinitely 
more  obvious  to  God  than  we  can  possibly  conceive 
them  to  be  to  material  beings. 

Yet  once  more,  we  know  that  reason  is  able  to  range 
beyond  the  action  of  the  senses.  Man  is  able  to  assure 
himself  that  events  have  happened  which  yet  have 
produced  no  direct  effect  upon  any  of  his  senses.  By 
the  exercise  of  reason  he  becomes  as  well  assured  of 
such  events  as  though  they  had  actually  passed  before 
his  eyes.  We  must  assume  that  an  analogous  power, 
but  infinite  in  degree,  infinitely  rapid  in  its  operation, 
and  infinite  in  the  extent  of  space  and  time  over  which 
it  ranges,  is  possessed  by  the  Almighty. 

And  now  let  us  notice  some  of  the  conclusions  to 
which  these  considerations  tend. 

Let  us  first  deal  with  the  teachings  of  that  sense 


312 


OTHER  WORLDS  THAN  OURS. 


whicli  is  the  most  far-reaching*  of  all  the  faculties 
given  to  man — the  sense  of  sight. 

In  a  little  treatise  called  "  The  Stars  and  the  Earth," 
published  anonymously  several  years  since,  some  re- 
sults of  modern  discoveries  respecting  light  were  dealt 
with  in  a  very  interesting  manner.  I  propose  to  fol- 
low the  path  of  thought  indicated  in  that  treatise,  as  a 
fitting  introduction  to  wider  conceptions  of  the  super- 
vision and  control  exercised  by  the  Almighty  over  his 
universe. 

We  know  from  Homer's  researches,  and  even  more 
surely  from  the  phenomenon  termed  the  aberration  of 
the  fixed  stars,  that  light  does  not  travel  with  infinite 
velocity.  Its  speed  is  indeed  so  enormous,  that,  com- 
pared with  every  form  of  motion  with  which  we  are 
familiar,  the  velocity  of  light  appears  infinitely  great. 
In  a  single  second  light  traverses  a  space  equal  to 
eight  times  the  circumference  of  the  earth  ;  and  there- 
fore, in  travelling  from  any  visible  object  on  the  earth 
to  the  eye  of  a  terrestrial  observer,  light  occupies  a 
space  of  time  indefinitely  short.  Yet,  even  as  regards 
such  objects  as  these,  light  has  occupied  a  real  interval 
of  time,  however  minute,  in  reaching  the  eye ;  inso- 
much that  we  see  objects  not  as  they  are  at  the  mo- 
ment we  perceive  them,  but  as  they  were  the  minutest 
fraction  of  a  second  before. 

*  Most  persons,  if  asked  which  sense  comes  next  to  sight  in  this  re- 
spect, would  answer  hearing.  Yet  touch — or  rather  feeling — has  a  range 
far  exceeding  that  of  hearing,  since  we  can  feel  the  heat  emitted  by  the 
sun.  Nor  is  it  difficult  to  conceive  of  such  an  increase  in  the  delicacy  of 
the  sense  of  touch,  that  even  the  minute  amount  of  heat  received  from 
the  iixed  stars  might  be  felt,  and  so  the  range  of  the  sense  extended 
many  million-fold. 


SUPERVISION  AND   CONTROL.  ^^ 

Eaising  our  eyes  from  the  earth  to  regard  the  celes- 
tial objects,  we  find,  in  place  of  the  indefinitely  minute 
interval  before  considered,  a  really  appreciable  space 
of  time  occupied  by  light  in  carrying  to  us  information 
as  to  the  condition  of  those  distant  orbs.  From  the 
moon,  light  takes  little  more  than  a  second  and  a 
quarter  in  reaching  us,  so  that  we  obtain  sufficiently 
early  information  of  the  condition  of  our  satellite. 
But  light  occupies  more  than  eight  minutes  in  reach- 
ing us  from  the  sun,  a  longer  or  shorter  interval  in 
travelling  to  us  from  Mercury,  Venus,  and  Mars,  ac- 
cording to  the  position  of  these  planets,  from  about 
thirty-five  to  about  fifty  minutes  in  reaching  us  from 
Jupiter,  about  an  hour  and  twenty  minutes  on  the 
average  in  speeding  across  the  great  gap  which  sepa- 
rates us  from  Saturn,  while  we  receive  intelligence 
from  Uranus  and  Neptune  only  after  intervals  respec- 
tively twice  and  three  times  as  great  as  that  which 
light  takes  in  reaching  us  from  the  ringed  planet. 

Thus,  if  we  could  at  any  instant  view  the  whole 
range  of  the  solar  system  as  distinctly  as  we  see  Jupi- 
ter or  Mars  when  in  opposition,  the  scene  presented  to 
us  would  not  indicate  the  real  aspect  of  the  solar  sys- 
tem at  that,  or  indeed  at  any  definite  instant.  Pre- 
cisely as  a  daily  newspaper  gives  us  a  later  account 
of  what  is  going  on  in  London  than  of  events  happen- 
ing in  the  provinces,  of  these  than  of  events  on  the 
Continent,  and  of  these  again  than  of  occurrences  tak- 
ing place  in  America,  Asia,  Africa,  or  Australasia,  so 
the  intelligence  brought  by  light  respecting  the  various 
members  of  the  solar  system  belongs  to  different  epocha 
H 


3H  OTHER    WORLDS  THAN  OURS. 

And  if  man  had  powers  of  vision  enabling  him  to  watch 
what  is  taking  place  on  the  different  planets  of  the  solar 
system,  it  is  clear  that  events  of  the  utmost  importance 
might  have  transpired — under  his  very  eyes,  so  to 
speak — while  yet  he  remained  wholly  unconscious  of 
their  recurrence.  Or,  to  invert  the  illustration,  if  an 
observer  on  Neptune  could  see  all  that  is  taking  place 
on  the  earth,  he  might  remain  for  hours  quite  uncon- 
scious of  an  event  important  enough  to  affect  the  we!  • 
fare  of  a  whole  continent,  though  that  event  should 
happen  under  his  eyes,  and  his  visual  powers  be  such 
as  I  have  supposed.  We  can  imagine,  for  example, 
an  observer  on  Neptune  watching  the  battle  of  Water- 
loo from  the  early  dawn  until  the  hour  when  Napo- 
leon's heart  was  yet  full  of  hope,  and  our  great  captain 
was  watching  with  ever-growing  anxiety,  as  charge 
after  charge  threatened  to  destroy  the  squares  on  whose 
steadfastness  depended  the  fate  of  a  continent.  We 
can  conceive  how  full  of  interest  that  scene  would  have 
been  to  an  intelligent  Neptunian,  and  how  eagerly  he 
would  have  watched  the  manosuvres  of  either  army, 
and  also,  what  neither  army  knew  of,  the  approach  of 
Blucher  with  his  Prussians.  Yet,  while  our  Nep- 
tunian would  thus  have  traced  the  progress  of  the  bat- 
tle from  his  distant  world,  the  conflict  would  in  reality 
have  been  long  since  decided,  the  final  charge  of  the 
British  army  accomplished,  the  Imperial  Guard  de- 
stroyed, Napoleon  fugitive,  and  the  Prussians,  who  to 
the  Neptunian  would  be  seen  still  struggling  through 
muddy  roads  toward  the  field  of  battle,  would  be  re- 
lentlessly pursuing  the  scattered  army  of  France. 


SUPERVISION  AND   CONTROL.  3,5 

It  is,  however,  when  we  pass  beyond  the  limits  of 
the  solar  system  that  the  non-contemporaneous  nature 
of  the  scene  presented  to  us  becomes  most  striking. 
Here  we  have  to  deal  not  with  seconds,  minutes,  or 
hours,  but  with  years,  decades,  and  centuries.  From 
the  nearest  of  the  fixed  stars  light  takes  fully  three 
years  in  travelling  to  the  earth.  Even  the  star  61 
Cygni  is  so  far  from  us  that  its  light  only  reaches  us  in 
ten  years.  And,  so  far  as  observation  has  hitherto 
gone,  it  seems  unlikely  that,  amid  the  whole  host  of 
heaven,  there  are  so  many  as  a  hundred  stars — lucid 
or  telescopic — whose  light  reaches  us  in  a  shorter  in- 
terval of  time  than  twelve  or  fifteen  years.  Whatever 
views  we  form  as  to  the  arrangement  of  the  sidereal 
scheme,  whether  those  usually  accepted  be  held  to  be 
correct,  or  whether  I  have  been  right  in  adopting 
others,  there  can  be  no  doubt  that,  among  the  stars 
revealed  to  us  by  the  telescope,  there  must  be  myriads 
which  lie  many  times  farther  from  us  than  the  bright 
star  in  Centaurus  and  the  orb  in  Cygnus  which  have 
been  found  relatively  so  near  to  us.  In  fact,  the  views 
I  have  adopted,  respecting  the  wide  range  of  magni- 
tude among  the  fixed  stars,  do  not  interfere  in  the 
least  with  the  theories  which  have  been  formed  as  to 
the  distances  from  beyond  which  the  light  of  some  of 
the  stars,  only  just  visible  in  powerful  telescopes,  must 
be  supposed  to  reach  us.  On  the  contrary,  one  may 
conceive,  according  to  my  views,  that  some  of  these 
faintly-seen  orbs  may  be  many  times  larger  even  than 
giant  Sirius,  in  which  case  the  distance  of  such  stars 
would  be  many  times  greater  than  has  been  hitherto 


p6  OTHER    WORLDS  THAN  OURS. 

supposed.  We  may  at  any  rate  assume  with  confi- 
dence that  many  stars  only  visible  in  powerful  tele- 
scopes  shine  from  beyond  depths  which  light  would 
occupy  thousands  of  years  in  traversing.  I  cannot, 
indeed,  go  further,  as  astronomers  have  hitherto  done, 
and  say  that  the  nebulae  must  be  regarded  as  external 
galaxies,  and  therefore  as  sending  their  light  to  us 
over  spaces  which  light  must  take  many  times  as  long 
an  interval  in  traversing  as  it  does  in  travelling  to  us 
from  the  bounds  of  our  own  galaxy.  But  it  would  be 
to  misinterpret  altogether  the  views  which  I  have 
formed  respecting  the  universe  to  suppose  that  I  ima- 
gine those  distant  spaces  which  astronomers  have 
hitherto  filled  with  imaginary  galaxies  to  be  unten- 
anted.  On  the  contrary,  I  have  no  doubt  whatever 
that  galaxies,  resembling  our  own,  exist  at  distances 
infinitely  exceeding  those  at  which  astronomers  have 
placed  their  most  distant  nebular  universes,  if  even 
the  bounds  of  our  own  galaxy  do  not  extend  into  space 
as  far  as  the  widest  limits  hitherto  assigned  to  the  sys- 
tem of  nebulae.  So  that  I  am  not  precluded  from 
speaking  of  orbs  whose  light,  though  unrecognized  by 
us,  yet  is  ever  pouring  in  upon  the  earth,  conveying, 
though  in  letters  we  cannot  decipher,  or  even  trace,  a 
message  which  has  taken  millions  on  millions  of  years 
in  traversing  the  awful  gulf  beyond  which  lie  those 
mysterious  realms. 

If  we  conceive,  then,  that  man's  visual  powers 
could  suddenly  be  so  increased  that,  without  instru- 
mental aid,  he  could  look  around  him  into  the  celes- 
tial depths,  piercing  even  to  those  outer  galaxies  which 


SUPERVISION  AND    CONTROL.  -17 

astronomers  have  seen  only  imaged  in  the  nebulae, 
how  wide  would  be  the  range  of  time  presented  to  him 
by  the  wonderful  scene  he  would  behold.  There 
would  blaze  out  Alpha  Centanri  with  its  record  three 
years  old ;  there  the  star  in  Cygnus  as  it  existed  ten 
years  since ;  the  whole  host  of  stars  known  to  man 
would  exhibit  records  ranging  from  a  few  years  to 
many  centuries  in  age ;  and,  lastly,  the  external  gal- 
axies, which  are  perhaps  forever  hidden  from  the 
searching  gaze  of  man,  would  reveal  themselves  as 
they  were  ages  on  ages  before  man  appeared  upon  the 
earth,  ages  even  before  this  earth  was  framed  into  a 
globe,  nay  ages  perhaps  before  the  planetary  system 
had  begun  to  gather  into  worlds  around  its  central 
orb. 

It  is  when  we  are  thus  contemplating  in  imagina- 
tion the  whole  expanse  of  the  universe,  and,  as  one 
may  almost  say,  the  whole  range  of  past  time,  that 
the  author  of  the  little  treatise  I  have  spoken  of  in- 
vites us  to  consider  two  processes  of  thought  having 
sole  reference  to  this  earth  on  which  we  live,  and  to 
that  history  which,  though  all-important  to  ourselves, 
seems  to  fade  into  such  utter  insignificance  in  the 
presence  of  the  grand  history  of  the  orbs  which  lie  in 
uncounted  millions  around  us. 

To  a  being  placed  on  some  far-distant  orb,  whence 
light  would  occupy  thousands  of  years  to  wing  its 
flight  to  us,  there  would  be  presented,  if  he  turned  his 
gaze  upon  our  earth,  and  if  his  vision  were  adequate 
to  tell  him  of  her  aspect,  the  picture  of  events  which 
thousands  of  years  since  really  occurred  upon  her  sur- 


jl8  OTHER   WORLDS  THAN  OURS. 

face.  For  the  light  which  left  the  earth  at  that  time, 
winging  its  way  through  space  with  the  account,  if  we 
may  so  speak,  of  those  occurrences,  is  now  travelling 
as  swiftly  as  when  it  left  our  earth,  but  amid  regions 
of  space  removed  from  us  by  a  light-journey  thou- 
sands of  years  in  duration.  And  thus,  to  the  observer 
on  this  distant  orb,  the  events  which  happened  in 
those  far-off  years  would  seem  to  be  actually  in  prog- 
ress. 

But  now  conceive  that  powers  of  locomotion  com- 
mensurate with  his  wonderful  powers  of  vision  were 
given  to  this  being,  and  that  in  an  instant  of  time  he 
could  sweep  through  the  enormous  interval  separating 
him  from  our  earth,  until  he  were  no  farther  from  us 
than  the  moon.  At  the  beginning  of  that  tremendous 
journey  he  would  be  watching  events  which  were 
occurring  thousands  of  years  since ;  at  its  close  he 
would  gaze  upon  the  earth  as  it  was  one  second  only 
before  he  undertook  his  instantaneous  flight;  so  that, 
in  the  course  of  his  journey,  he  would  gaze  upon  a 
succession  of  events  which  had  occurred  during  those 
thousands  of  years  upon  the  face  of  this  little  earth. 

The  other  conception  is  no  less  beautiful  and  strik- 
ing— I  may  remark,  also,  that  it  is,  in  a  scientific 
sense,  somewhat  more  exact.  Suppose  that  a  being 
armed  with  such  powers  of  vision  as  we  have  imagined 
should  watch  from  the  neighborhood  of  our  earth  the 
progress  of  some  interesting  event.  If  he  then  began 
to  travel  from  the  earth  at  a  rate  equal  to  that  at 
which  light  travels,  he  would  see  one  phase  of  the 
event  continually  present  before  him,  because  he  would 


SUPERVISION  AND   CONTROL.  31g 

always  be  where  the  light-message  recording  that  event 
was  actually  travelling.  By  passing  somewhat  less 
swiftly  away,  he  would  see  the  event  taking  place 
with  singular  slowness  ;  while  by  passing  away  more 
swiftly  he  would  see  the  event  occurring  in  inverted 
order.  Suppose,  for  example,  he  were  watching  the 
battle  of  Waterloo,  he  could  gaze  on  the  fine  picture 
presented  by  the  Imperial  Guard  as  they  advanced 
upon  the  English  army,  for  hours,  years,  nay,  for  cen- 
turies or  cycles ;  or  he  might  watch  the  whole  prog- 
ress of  the  charge  occurring  so  slowly  that  years  might 
elapse  between  each  step  of  the  advancing  column, 
and  the  bullets  which  mowed  down  their  ranks  might 
either  seem  unmoving,  or  else  appear  to  wend  their 
way  with  scarcely  perceptible  motion  through  the  air ; 
or,  finally,  he  might  so  wing  his  flight  through  space 
that  the  Guard  would  seem  to  retreat,  their  dead  men 
coming  to  life  as  the  bullets  passed  from  their  wounds, 
until  at  length  the  Old  Guard  would  be  seen  as  it  was 
when  it  began  its  advance,  in  the  assured  hope  of  de- 
ciding Waterloo,  as  it  had  decided  so  many  hard- 
fought  battles  for  its  imperial  chief. 

It  may  seem  hypercritical  to  notice  scientific  in- 
exactness in  ideas  professedly  fanciful.  But  as  the 
author  lays  some  little  stress  upon  the  scientific  truth 
of  the  method  in  which  his  fancies  are  exhibited,  and 
as,  further,  he  dwells  upon  two  of  the  more  obvious 
objections  to  the  first  conception,  it  may  be  well  to 
consider  a  further  objection,  which  enforces  on  us  a 
total  change  in  the  way  of  presenting  the  idea.  He 
remarks  that  the  being  he  has  conceived  to  be  borne 


j20  OTHER   WORLDS  THAN  OURS. 

toward  the  earth  through  a  distance  so  enormous, 
would  not  see  in  a  moment  the  whole  history  of  the 
earth  during  the  thousands  of  years  considered,  but 
only  the  history  of  that  hemisphere  which  was  turned 
toward  him ;  while,  further,  all  that  took  place  under 
roofs  or  under  cover  of  any  sort,  would  remain  unper- 
ceived  by  him.  But  there  is  a  more  serious  objection. 
Among  the  events  which  have  taken  place  during 
those  thousands  of  years,  have  been  thousands  of  revo- 
lutions of  this  earth  around  the  sun,  and  more  than 
three  hundred  and  sixty-five  times  as  many  rotations 
of  this  earth  upon  her  axis,  to  say  nothing  of  the  state- 
ly sway  of  the  earth  in  her  motion  of  precession.  So 
that  our  imaginary  observer  would  in  reality  see  the 
earth  whirling  with  inconceivable  rapidity  upon  its 
axis,  and  sweeping  with  even  more  tremendous  velo- 
city around  the  sun,  so  as  to  complete  thousands  of 
circuits  in  a  single  second.  He  would  see  clouds 
forming  and  vanishing  in  an  amazing  succession  of 
changes,  all  occurring  in  a  single  instant.  And,  even 
though  his  powers  of  vision  enabled  him  to  pierce  the 
cloud-envelope,  he  would  not  have  a  consecutive  pre- 
sentment of  the  various  events  occurring  in  any  part 
of  the  earth,  but  only  a  hap-hazard  succession  of  half 
days  for  each  portion  of  her  surface. 

However,  we  can  easily  see  that,  by  a  slight  modi- 
fication, the  beautiful  conception  of  our  author  can  be 
made  to  illustrate  one  mode  at  least  in  which  the 
events  occurring  upon  our  earth  may  be  conceived  to 
be  at  all  times  present  to  the  thoughts  of  the  Al- 
mighty. Imagine  a  sphere  with  a  radius  over  which 


SUPERVISION  AND   CONTROL.  32l 

jglit  would  travel  in  the  time  which  has  elapsed  since 
dving  creatures  first  began  to  move  upon  this  earth 
and  having  for  centre  the  place  occupied  by  the  earth 
at  that  instant.  Then,  if  we  imagine  millions  of  eyes 
over  the  surface  of  that  sphere,  all  turned  with  pier- 
cing powers  of  vision  upon  the  central  earth,  we  see 
that  to  these  eyes  the  earth  would  be  presented  by  the 
record  of  light,  not  as  she  is  now,  but  as  she  was  at 
that  primeval  day.  Now,  conceive  these  millions  of 
eyes  closing  swiftly  in  upon  the  earth,  but  with  this 
peculiarity  of  movement  that,  instead  of  being  always 
on  a  sphere  around  a  fixed  point,  they  were  always  on 
a  sphere  around  the  position  which  was  really  occu- 
pied by  the  earth,  when  the  light-messages  started 
which  those  eyes  are  receiving  at  the  moment.  Then 
if  that  wondrous  sphere  contracted  in  an  instant,  ac- 
cording to  the  law  assigned  it,  until  its  myriad  mill- 
ions of  eyes  were  gazing  intently  on  our  earth  from  a 
sphere  of  but  a  few  thousand  miles  in  radius,  the 
whole  history  of  the  earth,  so  far  as  light  could  render 
it,  would  have  been  in  a  moment  of  time  presented 
before  the  myriad-eyed  sphere. 

To  apply  this  illustration  to  the  subject  we  are 
upon.  We  know  that  the  Almighty  is  present  where 
the  boundary  of  our  great  sphere  was  placed  at  first. 
Before  Him  the  light-messages  are  presenting  the 
account  of  the  primeval  earth.  He  also  is  present 
everywhere  within  the  region  through  which  the  con- 
tracting sphere  was  conceived  to  pass.  He  therefore 
gees  the  whole  history  of  the  earth  as  presented  by  the 
light-waves.  We  begin,  however,  already  to  feel  that 


J22 


OTHER    WORLDS  THAN  OURS. 


we  cannot  say  of  Him  what  we  said  of  the  imaginary 
being  first  thought  of,  or  of  the  myriad-eyed  contract- 
ing sphere,  that  in  a  moment  of  time  He  can  see  the 
whole  history  of  the  earth  successively  presented  before 
Him.  As  He  exists  throughout  that  space,  there  is 
no  succession  of  time  in  His  vision  of  the  events  tran- 
spiring on  our  globe.  Past  and  present  are  one  before 
Him ;  and  we  shall  soon  see  that  present  and  future 
also  must  be  one  in  His  sight. 

But  now,  still  considering  only  the  information 
which  light  conveys  as  it  travels  onward  through 
space,  we  see  that  what  is  true  of  our  earth  is  true 
also  of  every  orb  throughout  the  universe.  The  whole 
light-history  of  every  such  orb  must  be  present  at 
every  instant  of  time  to  the  Creator  who  is  omni- 
present. So  that  to  the  obvious  conception  that  God, 
being  everywhere,  must  be  cognizant  of  all  things,  we 
have  to  add  this  further  consequence  of  His  omnipres- 
ence, that  He  must  be  cognizant  of  the  history  of 
all  things,  in  the  same  sense  that  a  man  is  cognizant 
of  events  which  are  passing  before  his  eyes. 

And,  by  extending  these  considerations  to  other 
modes  in  which  the  history  of  an  event  is  recorded,  so 
to  speak,  by  natural  processes,  we  can  see  that  a  much 
more  complete  and  definite  picture  of  past  events  than 
light  can  convey,  must  be  at  all  times  present  before 
the  Almighty.  A  sense  which  could  analyze  heat-im- 
pressions as  eyesight  analyzes  light,  would  tell  us  not 
only  what  eyesight  tells  us,  but  much  that  no  light- 
messages  can  convey  to  us.  At  least  it  is  conceivable 
that  a  sense  of  this  sort  would  enable  the  being  pro- 


SUPERVISION  AND   CONTROL.  ^ 

vided  with  it  to  recognize  not  merely  the  nature  of  the 
surface  of  any  body  whose  heat  reached  the  organ  of 
this  sense,  but  the  quality  of  the  body's  internal  struct- 
ure, processes  going  on  within  the  body,  or  the  nature 
of  bodies  so  placed  that  eyesight  would  not  render  us 
sensible  even  of  their  existence.  Electricity,  in  like 
manner,  would  avail  to  give  information  altogether 
distinct  from  that  which  light  can  impart.  And  pre- 
cisely as,  in  considering  light,  we  saw  that  the  Creator 
must  be  supposed  sensible  of  every  light-record  trav- 
elling through  space,  so,  as  regards  these  imaginary 
but  conceivable  senses,  we  must  believe  that  any  in- 
formation which  they  could  by  any  possibility  impart, 
must  be  conveyed  to  the  omnipresent  God.  And 
further,  it  would  be  a  contradiction  to  our  belief  in  His 
infinite  wisdom  to  suppose  that  the  infinite  multi- 
plicity of  the  records  thus  continually  present  before 
Him  could  in  any  way  render  their  significance  less 
distinct.* 

But,  turning  from  the  consideration  that  the  Al- 
mighty, by  virtue  of  His  omnipresence,  is  thus  cog- 
nizant, not  merely  of  all  that  is  at  any  moment  taking 

*  Moralizing  may  seem  altogether  out  of  place  in  such  a  work  as  this, 
but  certainly  one  is  tempted  to  dwell  somewhat  thoughtfully  on  the 
ideas  raised  by  the  considerations  I  have  dwelt  on  above.  It  is  not  with- 
out a  feeling  of  awe  that  one  considers  that  the  records  of  every  action 
of  our  lives  are  not  merely  at  this  moment  before  God,  but  will  for  ever 
and  ever  be  freshly  present  to  Him :  and  that,  not  merely  in  the  sense 
that  He  knows  every  thing  (an  idea  too  vague  for  man  rightly  to  grasp), 
but  by  the  action  of  physical  processes  such  as  our  Faradays  and 
Tyndalls  deal  with.  May  it  not  be  through  an  instinctive  recognition 
of  this  great  truth,  that  man  alone,  of  all  the  creatures  which  people 
this  earth,  feels  contrition  for  long-past  misdeeds,  even  where  be  has  no 
fear  of  their  ever  bearing  fruit  in  future  sorrows? 


524 


OTHER  WORLDS  THAN  OURS. 


place  throughout  the  universe,  but  of  all  that  has 
taken  place  in  the  infinity  of  past  time,  we  have  to 
consider  another  mode  in  which  the  universe  must  be 
regarded  as  present  before  Almighty  God. 

The  senses  by  which  we  judge  of  what  is  going  on 
around  us  are,  after  all,  merely  one  means  by  which  we 
judge  of  causes  by  their  effects.  "When  we  say,  for 
instance,  that  we  have  seen  such  and  such  an  object, 
or  watched  such  and  such  an  event,  what  we  really 
imply  is,  that  we  have  recognized  certain  physical  im- 
pressions, which  we  can  only  explain  by  the  existence 
of  that  object,  or  by  the  occurrence  of  that  event. 
We  know,  in  fact,  that  in  certain  exceptional  cases  im- 
pressions resembling  those  caused  by  the  actual  pres- 
ence of  an  object,  or  by  the  actual  occurrence  of  some 
event,  may  arise  where  no  such  object  has  been  present, 
or  where  no  such  event  has  transpired.  Still,  we 
commonly  feel  safe  from  error,  in  concluding,  from 
certain  impressions  conveyed  to  the  mind  by  the  agen- 
cy of  the  visual  organs,  that  certain  objects  have  been 
really  present,  at  rest  or  in  action,  before  us. 

But,  then,  even  man,  limited  as  are  his  powers,  can 
yet  follow  a  series  of  effects  and  causes  far  more  nu- 
merous than  those  concerned  in  the  act  of  vision  ;  and 
so  he  can  become  certain  of  the  occurrence  of  past 
events  of  which  no  sense  he  possesses  gives  him  any 
direct  information.  For  example,  though  I  neither 
saw  the  battle  of  Waterloo  nor  heard  the  thunder  of 
the  guns  there,  yet  I  am  as  certain  that  the  battle 
really  took  place  as  though  sight  and  hearing  had 
given  me  direct  information  on  the  matter.  And, 


SUPERVISION  AND   CONTROL.  ^ 

tvhen  I  inquire  whence  that  certainty  arises,  I  find  a 
complicated  series  of  events  involved  in  my  acqui- 
sition of  the  knowledge  that  the  battle  took  place. 
My  interpretation  of  the  letter-press  account  of  the 
battle  involved  in  itself  a  number  of  more  or  less  com- 
plex relations,  associated  with  the  question  of  my  con- 
fidence in  those  who  taught  me  that  certain  symbols 
represented  certain  letters,  that  certain  combinations  of 
letters  represented  certain  words,  and  that  certain  words 
represented  certain  ideas.  Not  to  follow  out  the  long 
train  of  ideas  thus  suggested,  it  will  be  clear  that,  with 
regard  to  a  variety  of  matters,  the  knowledge  which 
any  man  has  is  associated  with  considerations  of  cause 
and  effect,  of  general  experience,  of  confidence  in  the 
accounts  of  others  or  in  his  own  judgment,  which  are 
in  reality  of  a  highly-complex  character. 

Now,  we  are  led  by  these  thoughts  to  remember 
that,  independently  of  those  records  of  past  events 
which  are  brought  continually  before  the  Almighty 
by  processes  resembling  those  which  directly  affect 
our  senses,  such  events  must  be  recognizable  by  Him 
(even  to  their  minutest  details)  in  the  consequences 
which  they  have  led  to.  If  a  great  naturalist  like 
Huxley  or  Owen  can  tell,  by  examining  the  tooth  of  a 
creature  belonging  to  some  long-extinct  race,  not  only 
what  the  characteristics  of  that  race  were,  but  the  gen- 
eral nature  of  the  scenery  amid  which  such  creatures 
lived,  we  see  at  once  that  a  single  grain  of  sand  or 
drop  of  water  must  convey  to  the  Omniscient  the  his- 
tory of  the  whole  world  of  which  it  forms  part.  Nay, 
why  should  we  pause  here  ?  The  history  of  that  world 


p6        OTHER  WORLDS  THAN  OURS. 

is  in  truth  bound  up  so  intimately  with  the  history  of 
the  universe,  that  the  grain  of  sand  or  drop  of  water 
conveys  not  only  the  history  of  a  world,  but  with  equal 
completeness  the  history  of  the  whole  universe. 

The  Almighty,  then,  by  virtue  of  His  possessing  in 
an  infinite  degree  that  quality  which  enables  man  to 
reason  upon  past  events  of  which  his  senses  bring  him 
no  direct  intelligence,  has  the  whole  past  history  of  the 
universe  continually  present  before  Him,  in  the  state 
and  position  of  each  single  atom  throughout  infinity 
of  space.* 

Turning  from  the  past  to  the  future,  we  must  not 
let  the  limited  nature  of  our  recognition  of  the  course 
of  future  events  prevent  us  from  forming  a  just  opin- 
ion as  to  the  way  in  which  the  future  must  be  always 
present  before  God.  We  can  judge  of  the  past  by  its 
effects,  but  we  are  almost  utterly  unable  to  judge  of  the 
future  by  its  causes.  Yet  we  cannot  doubt  that  the 
future  is  present  in  its  germs,  precisely  as  the  past  is 
present  in  its  fruits.  It  may  be  regarded  in  fact  as 
merely  a  peculiarity  of  man's  constitution  that  the 
past  is  more  clearly  present  to  his  mental  vision  than 
the  future.  It  is  easy  not  only  to  conceive  that  the 
future  and  the  past  should  be  equally  present  to  intel- 
ligent creatures,  but  to  conceive  of  a  form  of  intelli- 
gence according  to  which  past  events  would  be  obliter- 
ated from  the  mind  as  fast  as  they  took  place,  while 

*  In  fact,  if  we  consider  the  matter  attentively,  we  see  that  there 
cannot  be  a  single  atom  throughout  space  which  could  have  attained  its 
present  exact  position  and  state,  had  the  history  of  any  part  of  the  uni- 
verse, however  insignificant,  been  otherwise  than  it  has  actually  been,  in 
even  the  minutest  degree. 


SUPERVISION  AND   CONTROL.  327 

the  future  should  be  as  actually  present  as  to  the  ordi- 
nary human  mind  the  past  is. 

In  considering  the  Omniscient,  however,  all  ques- 
tions of  degree  must  be  set  on  one  side.  The  future 
must  be  as  absolutely  and  essentially  present  to  Him 
in  its  germs  as  the  past  has  been  shown  to  be  in  its 
fruits.  If  a  grain  of  sand  contains  in  its  state,  figure, 
and  position,  the  picture  of  the  universe  as  it  is,  and 
the  whole  history  of  the  universe  throughout  the  infi- 
nite past — and  who  can  doubt  that  this  is  so? — it  con- 
tains with  equal  completeness  the  history  of  the  uni- 
verse throughout  the  infinite  future.  No  other  view 
is  compatible  with  the  assumption  of  the  Almighty's 
infinite  wisdom,  and  no  assumption  which  limits  the 
wisdom  of  God  is  compatible  with  our  belief  that  He 
is  supreme  in  the  universe. 

Obviously  also  every  event,  however  trifling,  must 
be  held  to  contain  in  itself  the  whole  history  of  the 
universe  throughout  the  infinite  past,  and  throughout 
the  infinite  future.  For  every  event,  let  its  direct 
importance  be  what  it  may,  is  indissolubly  bound  up 
with  events  preceding,  accompanying,  and  following  it, 
in  endless  series  of  causation,  interaction,  and  effect. 

So  far,  then,  as  the  Almighty's  watch  over  His 
universe  is  concerned,  we  have  two  lines  of  thought, 
each  leading  to  the  recognition  of  a  perfect  super- 
vision. In  virtue  (1)  of  His  omnipresence,  and  (2)  of 
His  infinite  wisdom,  He  sees  at  each  instant  the  whole 
universe  as  it  has  been  in  the  infinite  past,  as  it  is  now, 
and  as  it  will  be  in  the  infinite  future ;  and  this  being 
as  true  of  any  one  instant  as  it  is  of  any  other,  we 


3 28  OTHER   WORLDS  THAN  OURS. 

recognize  the  operation  of  yet  a  new  form  of  infinity — 
the  infinite  duration  of  the  Almighty's  existence — to 
render  yet  more  inconceivably  perfect  God's  super- 
vision of  His  universe. 

And  now  with  regard  to  control.  Does  the  Al 
mighty,  who  supervises  all  things,  exercise  any  con- 
trolling action  upon  the  course  of  events  ? 

It  need  hardly  be  said  that,  if  God  does  exercise 
control,  apart  from  the  laws  which  He  has  assigned  to 
His  universe,  His  knowledge  of  the  progress  of  past 
and  future  events  is  not  therefore  to  be  called  in  ques- 
tion, since  His  own  direct  action,  whether  in  the  past 
or  in  the  future,  is  quite  as  much  the  subject  of  His 
consciousness  (to  use  this  word  for  want  of  a  better)  as 
the  action  of  His  creatures  or  of  the  laws  He  has  pri- 
marily set  them. 

We  know  that  certain  laws  have  been  assigned  to 
the  universe,  and  we  know  also  that,  so  far  as  our 
very  limited  experience  enables  us  to  determine,  these 
laws  are  never  abrogated.*  Here  I  set  altogether 

*  All  things  working  thus  according  to  law,  however,  certain  diffi- 
culties suggest  themselves  which  must  not  be  left  undealt  with,  since 
not  to  consider  them  might  be  to  leave  painful  doubts  in  the  minds  of 
some  who  may  read  these  pages. 

In  the  first  place,  there  is  the  old  question  of  the  relation  between 
man's  free-will  and  the  absolute  foreknowledge  of  Almighty  God.  It 
seems  clear  to  many  that  if  all  things  are  foreknown  there  can  be  no 
such  thing  as  free-will ;  insomuch  that  some  have  even  felt  forced  to 
believe  that  the  Almighty,  though  undoubtedly  omniscient,  must  in  a 
sense  forego  His  knowledge  of  future  events  so  that  the  actions  of  men 
may  be  subject  to  the  control  of  their  will  But  in  reality  we  have 
only  to  consider  the  analogy  of  human  foreknowledge,  to  see  that  there 
is  no  necessity  for  any  theory  so  self-contradictory  as  this.  We  have 
already  considered  other  attributes  of  the  Almighty  as  in  a  sense  re- 


SUPERVISION  AND   CONTROL.  ^29 

aside,  for  the  moment,  the  possibility  of  miracles,  and 
consider  only  the  results  of  experimental  or  observa- 
tional science.  Thus,  we  are  led  to  the  conclusion 
that  all  things  happen  according  to  set  physical  laws; 

sembling,  though  infinitely  exceeding  in  range  of  action,  certain  attri- 
butes of  man  ;  let  us,  then,  inquire  whether  that  attribute  of  man  which, 
though  imperfect  and  limited,  yet  corresponds  to  the  foreknowledge  of 
God,  affords  us  any  reason  for  believing  that  perfect  foreknowledge  bare 
the  exercise  of  free-will.  The  answer  is  obvious  at  once.  We  know- 
that  we  often  judge,  with  more  or  less  certainty  of  conviction,  that  such 
and  such  acts  will  be  performed  by  others,  and  that  yet  our  anticipation 
in  no  sense  influences  the  will  of  the  persons  who  are  expected  so  to 
act  Suppose  I  remember,  for  example,  that  I  have  left  a  valuable 
in  a  room  which  will  presently  be  passed  through  by  one  whom  I  know 
to  be  dishonest ;  I  judge  accordingly  that  the  person  will  purloin  the 
valuable.  In  this  case  his  free-will  is  not  affected  by  my  anticipation ; 
nor  would  it  be  though  a  yet  clearer  conviction  of  his  conduct  were  im- 
pressed upon  me.  There  is,  in  fact,  no  conceivable  degree  of  certainty 
on  my  part  which  would  render  him  undeserving  of  punishment  for 
stealing  the  valuable.  And  so,  not  to  give  further  instances  where  the 
matter  is  so  obvious,  we  see  that  no  conceivable  degree  of  foreknowl- 
edge bars  free-will.  The  infinite  and  absolute  foreknowledge  of  the 
Almighty  is  therefore  altogether  dissociated  from  the  dangerous  and 
hurtful  belief  in  a  predestination  which  renders  man  irresponsible  for 
his  actions. 

Secondly,  the  belief  in  the  absolute  perfection  of  the  laws  according 
to  which  God  rules  His  universe,  insomuch  that  throughout  all  the 
worlds  in  space  all  things  work  according  to  those  laws  without  need 
of  special  interference  on  His  part,  has  been  thought  by  many,  and  is 
painfully  felt  by  some,  to  oppose  itself  to  our  belief  in  the  efficacy  of 
prayer.  In  touching  on  this  point,  I  wish  very  carefully  to  avoid  any 
intrusion  on  matters  apart  from  the  general  scope  of  my  subject ;  but  a 
few  words  may  be  permitted  me  on  a  point  which  comes  close  home  to 
the  hearts  of  all  of  us,  and  which  also  does  seem  in  a  sense  associated 
with  the  matters  I  have  been  dealing  with.  All  men,  I  suppose,  pray; 
though  many  may  in  words  deride  prayer,  and  though  hundreds,  without 
expressing  doubts,  may  fail  to  see  any  possible  utility  in  the  practice, 
because  they  cannot  believe  that  the  action  of  the  physical  laws  of  God 
can  be  interfered  with  in  answer  to  the  appeal  of  His  creatures.  It  is 
because  I  fear  lest  some  of  my  readers  should  have  felt  this  difficulty, 


33° 


OTHER    WORLDS  THAN  OURS. 


and  without,  by  any  means,  adopting  the  view  that  the 
Almighty  exercises  no  special  control  over  His  uni- 
verse, we  see  strong  reason  to  believe  that  the  laws 
which  He  has  assigned  to  it  are  sufficient  for  the  con- 

and  should  find  their  doubts  confirmed  by  any  thing  I  may  here  have 
written,  that  I  indicate  the  explanation  which  I  suppose  every  one  who 
thinks  much  upon  this  point  would  probably  be  led  to.  Remembering 
that,  on  the  one  hand,  it  is  unreasonable  to  conceive  that  God  would 
have  allowed  a  belief  in  the  efficacy  of  prayer  to  grow,  as  it  has  done, 
to  be  a  part  of  human  nature,  were  that  belief  founded  in  a  monstrous 
fiction,  and  tha*  on  the  other  hand,  it  is  unreasonable  to  suppose  that 
physical  laws  are  interfered  with  in  response  to  the  millions  of  prayers 
daily  offered  by  men,  the  obvious  conclusion  seems  to  be  that  prayers 
are  responded  to  (where  it  has  seemed  fitting  that  they  should  be)  with- 
out interference  with  natural  laws ;  that,  in  fact,  the  scheme  of  the  Al- 
mighty includes  at  once  the  prayers  and  their  response.  It  seems  baf- 
fling, indeed,  to  human  thoughts  that  such  an  infinity  of  varied  interests 
should  thus  be  provided  for,  in  a  scheme  whose  extent  covers  the  infini- 
ty of  past  and  future  time  ;  but  where  infinite  wisdom  is  in  question  this 
consideration  need  not  trouble  us.  Nor  is  this  particular  mode  of  con- 
trol inconsistent  even  with  our  merely  human  conceptions  of  what  is 
reasonable.  For  instance,  a  father,  desirous  at  once  of  testing  and  re- 
warding the  obedience  of  a  son,  might  tell  him  to  go  to  such  a  place 
and  to  open  such  a  box,  having  beforehand  placed  therein  a  reward  for 
his  son's  obedience.  Here  the  fulfilment  of  the  father's  request  would 
no  more  result  in  bringing  the  gift  to  the  box,  than  our  fulfilment  of  the 
duty  of  prayer  can  cause  the  laws  of  Nature  to  cease  or  change  in  their 
operation ;  yet  obedience  would  in  the  one  case,  as  we  can  conceive  it 
does  in  the  other,  in  reality  bring  about  its  own  reward.  And,  further, 
it  may  be  remarked  that,  precisely  as  the  greater  or  less  certainty  of  the 
father  as  to  his  son's  obedience  would  hi  no  sense  affect  the  latter's 
merit,  so  neither  does  the  absolute  foreknowledge  of  God  as  to  the 
prayers  which  His  creatures  will  offer  up,  affect  in  any  sense  the  merit 
which  He  has  been  pleased  to  recognize  in  the  sincere  performance  of 
the  act  of  prayer. 

Lastly,  there  is  the  difficulty  as  to  our  belief  in  miracles — that  is,  in 
events  which  involve  the  temporary  suspension  or  alteration  of  natural 
laws.  It  must  be  remembered  here  that  recent  physical  researches, 
though  they  have  enabled  us  to  interpret  so  many  of  the  laws  of  Nature, 
yet  tell  neither  for  nor  against  our  recognition  of  the  possibility  of 


SUPERVISION  AND   CONTROL. 


33» 


trol  of  all  things.  Indeed,  so  far  as  all  things  take 
place  in  accordance  with  laws  which  the  Almighty 
must  assuredly  have  Himself  ordained,  we  may  say 
that  every  event  which  has  happened  or  will  happen 
throughout  infinite  time  is  the  direct  work,  and  indi- 

miracles.  It  belongs  to  the  very  essence  of  a  miracle  that  it  should  be 
an  event  which  no  physical  researches  can  explain,  or  indeed  can  affect 
otherwise  than  to  render  it  the  more  inexplicable.  The  question  is,  not 
whether  such  and  such  an  event  is  more  or  less  wonderful  to  the  un- 
learned Hodge  or  Styles  on  the  one  part,  or  to  a  Newton  or  a  Faraday 
on  the  other,  but  whether  an  event  can  really  take  place  in  which  the 
laws  of  Nature  have  absolutely  been  annulled  and  abrogated.  I  take  it, 
for  instance,  that  if  we  could  see  a  hungry  multitude  fed  with  a  few 
loaves,  and  were  absolutely  certain  that  so  many  thousands  had  been 
satisfied  with  what  would  naturally  be  the  food  but  of  a  few,  our  wonder 
would  not  be  greater  or  less  whether  we  viewed  the  matter  as  a  laborer 
would,  who  simply  knows  what  hunger  is  and  what  is  needed  to  satisfy 
it,  or  whether  we  were  familiar  with  the  analysis  of  bread  and  com- 
parted  the  amount  of  fibrine  and  albumen  contained  in  the  loaves  with 
what  we  knew  of  the  daily  or  hourly  exhaustion  of  the  corresponding 
materials  in  the  human  frame. 

The  arguments  in  favor  of  miracles  or  against  their  having  occurred 
(of  their  possibility  there  need  be  no  question)  are  the  same  now  as  they 
were  in  less  scientific  ages.  Those  who  believe  in  the  occurrence  of 
miracles  argue  thus :  Man  differs  from  all  other  terrestrial  creatures 
in  being  responsible  to  his  Creator.  Thus  between  him  and  Almighty 
God  there  is  a  direct  relation,  which  renders  it  necessary  that  the  will 
of  God  should  be  communicated  to  man.  Now,  we  can  conceive  no  way 
in  which  such  communication  can  be  made  in  an  unmistakable  manner, 
but  by  events  which  involve  an  unmistakable  exercise  of  a  power  be- 
longing  to  God  alone — that  is,  by  events  of  a  supernatural  character. 
The  believer  in  miracles  further  argues  that  nothing  tending  to  prove 
the  impossibility  (in  a  natural  sense)  of  an  event  of  this  sort  can  be  ac- 
cepted to  disprove  its  occurrence,  since  what  is  essentially  requisite  to 
the  very  purpose  of  a  miracle  is  that  it  should  be  in  a  natural  sense  im- 
possible. Nor  is  it  necessary  that  any  recorded  miracle  should  be  in 
itself  of  a  striking  or  imposing  character,  so  long  as  its  connection  with 
the  communication  of  God's  will  in  a  special  manner  is  reasonabl} 
established,  since  the  triviality  or  non-triviality  of  an  event  whost 
miraculous  character  is  in  question  is  to  be  judged  only  by  the  circum- 


33* 


OTHER   WORLDS  THAN  OURS. 


cates  the  direct  purpose  and  will,  of  Almighty  God. 
Nor  need  the  thought  that  the  Almighty  thus  seems  to 
be  made  the  author  of  evil  as  well  as  of  good  in  any  way 
startle  us,  because  we  know  that  what  constitutes  evil 
or  good  in  our  limited  vision  may  by  no  means  be  ac- 
cepted as  indicative  of  what  is  evil  or  good  as  the  work 
of  God.  We  know,  limited  as  our  wisdom  is,  that  evil 
often  works  to  good,  so  that  if  the  Almighty,  whose 
wisdom  extends  over  the  never-ending  chain  of  sequent 
events,  seems,  by  permitting  evil,  to,  in  a  sense,  coun- 
tenance it,  we  are  to  recognize  the  sequent  good  as  in 
truth  His  work,  and. to  regard  that  which  is  objectively 
evil  (and  actually  evil  in  the  creature  who  does  it)  as 
subjectively  good  in  Him  who  permits  it  with  a  per- 
fect knowledge  of  all  that  in  the  infinity  of  future  time 
is  to  flow  from  it. 

Now,  it  seems  conceivable  that  in  reality  it  is  only 
our  limited  acquaintance  with  the  operation  of  the 
laws  which  God  has  set  His  universe,  which  makes  us 
regard  them  as  unchanging,  and,  so  to  speak,  inex- 
orable. There  seems,  indeed,  reason  rather  to  expect 

stances  of  those  for  whose  instruction  the  miracle  is  supposed  to  have 
been  worked. 

The  argument  against  the  occurrence  of  miracles  has  been  already 
considered.  As  has  been  pointed  out,  it  not  only  does  not  meet  the 
argument  just  stated,  but  rests  on  the  very  fact  which  constitutes  the 
basis  of  that  argument  —  the  fact,  namely,  that  the  occurrence  of 
miracles  is  contrary  to  experience.  It  is  obvious,  then,  that  the  con- 
siderations I  have  urged,  as  to  the  nature  of  God's  control  over  His 
universe,  need  not  be  regarded  as  in  the  slightest  degree  affecting  the 
belief  of  men  hi  those  direct  relations  between  God  and  man  which 
have  been  held  to  involve  the  necessity  of  miracles.  To  speak  further, 
however,  on  this  matter  would  bring  me  to  deal  with  that  subject  which 
I  have  selected  to  avoid 


SUPERVISION  AND   CONTROL.  333 

than  to  deny,  that  He  who  made  the  laws  may  annul 
or  suspend  them  at  His  pleasure. 

But  I  think,  that  this  view — though  it  has  been 
entertained  by  many  thoughtful  men,  especially  be- 
cause it  seems  to  give  the  Almighty  a  special  control- 
ling power  over  His  universe — is  in  reality  inconsistent 
with  just  conceptions  of  His  infinite  wisdom.  If  His 
wisdom,  though  inconceivably  great,  were  yet  finite, 
we  could  not  suppose  that  the  universe  would  have 
been  so  planned  (still  to  use  inexact  words  for  want  of 
better),  and  laws  of  such  a  nature  assigned  to  it,  that 
throughout  the  infinity  of  time  all  things  should  work 
out  the  will  and  purpose  of  Almighty  God.  There 
would  then,  undoubtedly,  be  continual  need  of  adap- 
tation, change,  remodelling — of  the  annulment  of  a 
law  here,  or  its  suspension  there — in  order  that  the 
whole  might  not  fall  to  wrack.  But  where  the  God 
of  JSTature  is  infinitely  wise,  there  can  be  no  such  neces- 
sity. The  whole  scheme  of  the  universe  must  needs 
be  so  perfect  that  direct  intervention  cannot  at  any 
time  be  required. 

To  sum  up,  we  find  ourselves  led  to  the  belief  that, 
while  intervention  with  the  operation  of  natural  laws 
is  unnecessary,  all  the  worlds  existing  throughout  space 
are,  in  a  very  definite  and  special  manner,  watched 
over  and  controlled  by  an  omnipresent,  omnipotent, 
and  omniscient  Being;  that  before  Him  the  infinite 
past  and  the  infinite  future  of  the  universe  are  at  all 
times  sensibly  present ;  that  each  the  minutest  atom 
and  every  the  least  important  event  exhibits  before 
Him  at  each  instant  the  perfect  history  of  the  limitless 


334 


OTHER    WORLDS  THAN  OURS. 


past  and  future  of  the  universe ;  and  lastly,  that  Hie 
infinitely  perfect  consciousness  of,  and  control  over,  all 
that  has  been,  is,  or  will  be,  are  infinitely  multiplied 
(to  use  the  only  available  expression)  by  the  infinite 
duration  throughout  which  His  existence  extends. 


HIE    END. 


WORKS  ON  ASTRONOMY. 


Elements  Of  Astronomy.     By  ROBERT  STOWELL  BALL,  LL.  D., 

F.  R.  S.,  Andrews  Professor  of  Astronomy  in  the  University  of  Dub- 
lin, Royal  Astronomer  of  Ireland.  With  Illustrations.  16mo.  Cloth, 

$2.25. 

Elementary  Lessons  in  Astronomy.     By  J.  NORMAN 

LOCKYER,  F.  R.  S.  Richly  illustrated,  and  embracing  the  Latest  Dis- 
coveries. American  edition.  Adapted  to  the  Schools  and  Academies 
of  the  United  States.  12mo.  Cloth,  $1.50. 

Outlines  Of  Astronomy.     By  Sir  J.  J.  W.  HERSCHEL.     With 

Plates  and  Woodcuts.    Eleventh  edition.     8vo.     Cloth,  $4.00. 

The  Sun.  By  C.  A.  YOUNG,  Ph.  D.,  LL.  D.,  Professor  of  Astronomy 
in  the  College  of  New  Jersey.  With  numerous  Illustrations.  12mo. 
Cloth,  $2.00. 

"  Professor  Toting  is  an  authority  on  '  The  Sun,'  and  writes  from  intimate 
knowledge.  He  has  studied  that  great  luminary  all  his  life,  invented  and  im- 
proved instruments  for  observing  it,  gone  to  all  quarters  of  the  world  in  search 
of  the  best  places  and  opportunities  to  watch  it,  and  has  contributed  important 
discoveries  that  have  extended  our  knowledge  of  it."— Popular  Science  Monthly. 

Spectrum  Analysis,  in  its  Application  to  Terres- 
trial Substances,  and  the  Physical  Constitu- 
tion Of  the  Heavenly  Bodies.  Familiarly  explained 
by  Dr.  H.  SCHELLEN,  Director  der  Realschule  I.  0.  Cologne.  Trans- 
lated from  the  second  enlarged  and  revised  German  edition  by  JANE 
and  CAROLINE  LASSELL.  Edited,  with  Notes,  by  WILLIAM  HFOGINS, 
LL.  D.  With  numerous  Woodcuts,  Colored  Plates,  and  Portraits ; 
also,  Angstrom's  and  Kirchhoff's  Maps.  8vo.  Cloth,  $6.00. 

"  This  admirable  work  does  credit  to,  or  should  we  Bay  is  worthy  of.  thn 
author,  the  translators,  and  the  editor.  The  first  part  treats  on  the  artificial 
sources  of  high  degrees  of  heat  and  light:  the  second  on  Spectrum  Analysis  in 
its  application  to  the  heavenly  bodies.  We  must  approve  the  method  followed 
in  the  translation  and  by  the  editor.  In  manv  translations  the  views  of  the 
author  are  suppressed,  in  order  that  the  views  of  the  translator  or  editor  may  bo 
expounded:  but  here  Dr.  Hnirgins,  however  leniently  such  a  fanlt  might,  have 
been  looked  upon  with  him,  has  permitted  the  author's  views  to  remain  intact, 
clearly  stating  his  own  and  wherein  lies  the  difference." — The  Chemical  Newt. 

"  Certainly,  as  regards  mere  knowledge,  the  '  Spectrum  Analysis'  has  let  us 
into  many  secrets  of  the  physical  universe  which  Newton  and  Laplace  would  have 
declared  impossible  for  man's  intellect  to  attain.  The  science  is  still  in  its  in- 
fancy, hut  it  is  prosecuted  by  some  of  the  ablest,  most  patient,  and  most  enthu- 
siastic observers,  and  some  of  the  keenest  thinkers,  at  present  existing  on  our 
little,  insignificant  physical  globe."— Boston  Globe.  ,  HBXT  PAGK.] 


WORKS  ON  ASTRONOMY.— (Continued.) 


Studies  in  Spectrum  Analysis.  By  J.  NORMAN  LOCKYER, 
F.  R.  S.,  Correspondent  of  the  Institute  of  France,  etc.  With  Sixty 
Illustrations.  12mo.  Cloth,  $2.50. 

"The  study  of  spectrum  analysis  is  one  fraught  with  a  pcfculi'ir  fascination, 
nnd  some  of  the  author's  experiments  are  exceedingly  picturesque  in  their  re- 
sults. They  are  so  lucidly  described,  too,  that  the  reader  keeps  on.  from  page 
to  page,  never  flagging  in  interest  in  the  matter  before  him,  nor  putting  down 
the  book  until  the  last  page  is  reached." — Aew  York  Evening  S&pmt, 

Origin  of  the  Stars,  and  the  Causes  of  their  Mo- 
tions and  their  Light.  By  JACOB  ENNJS.  12mo.  Cloth, 
$2.00. 

Astronomy  and  Geology  Compared.    By  Lord  OKMA- 

THWAITE.     18mo.     Tinted  paper.     Cloth,  $1.00. 

The  Expanse  Of  Heaven.  A  Series  of  Essays  on  the  Won- 
ders of  the  Firmament.  By  R.  A.  PROCTOR.  12mo.  Cloth,  $2.00. 

"  '  The  Expanse  of  Eeaven '  can  not  fail  to  be  of  immense  use  In  forwarding 
the  work  of  education,  even  when  it  is  read  only  for  amusement,  so  forcible  is  the 
impression  it  makes  on  the  mind  from  the  importance  of  the  subjects  treated  of, 
while  the  manner  of  treatment  is  BO  good."— .Boston  Tiaveller. 

The  Moon  :  Her  Motions,  Aspect,  Scenery,  and  Physical  Conditions, 
with  Two  Lunar  Photographs  and  many  Illustrations.  By  R.  A. 
PROCTOR.  New  edition.  12.no.  Cloth,  $3.50. 

Other  Worlds  than  Ours  ;  the  Plurality  of  Worlds,  studied 
under  the  Light  of  Recent  Scientific  Researches.  By  R.  A.  PROCTOR. 
With  Illustrations,  some  colored.  12mo.  Cloth,  $2.50. 

Our  Place  among  Infinities.  A  Series  of  Essays  contrasting 
our  Little  Abode  in  Space  and  Time  with  the  Infinities  around  us. 
To  which  are  added  Essays  on  the  Jewish  Sabbath  and  Astrology. 
By  R.  A.  PROCTOR.  12mo.  Cloth,  $1.75. 


For  sale  by  all  booksellers;  or  sent  by  mail,  post-paid,  on  receipt  of  price. 


New  York :  D.  APPLETON  &  CO.,  1,  3,  &  5  Bond  Street. 


Date  Due 


•TGI 

DEC  1  7  197 

3 

i&WV 

'C  1  o'  1973' 

*          1U> 

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* 

RECD     JUr 

i 

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m 

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